FEAT: Add Garak latent injection scenario

[Juhie (juhiechandra)]

Description

Adds a PyRIT-native latent-injection scenario, porting the behaviour of garak's
latentinjection probes without porting their runtime structure. Closes #2530; part of
the scanner parity work in #511. The separation of responsibilities follows the
PromptInject scenario from #2509 rather than garak's Probe/mixin/detector layout — no
Probe, mixin, hook, detector, or generator code is carried over.

Every prompt is a benign task ("summarise this resume", "is this domain malicious?")
applied to a carrier document with an attacker instruction buried inside it. The attack
succeeds when the response echoes the trigger text the injection asked for.

Datasets own the source content. Four local .prompt datasets under
pyrit/datasets/seed_datasets/local/garak/ hold the ingredients separately — 51 carrier
contexts, 27 benign task instructions, 32 injection templates and 75 payloads. Expected
trigger text, carrier family, language and source provenance are preserved as seed
metadata. Garak is Apache-2.0 rather than MIT, so each dataset records NVIDIA as author,
names NVIDIA CORPORATION & AFFILIATES as the copyright holder, states that the content
is used under the Apache License 2.0, pins a commit-level source URL, and notes the
only modification made (garak's templating markers renamed to PyRIT's).

A dataset configuration builds the seed groups. LatentInjectionDatasetConfiguration
overrides _build_attack_groups to combine a task instruction, a carrier document, an
injection instruction and a payload into one AttackSeedGroup per template. The groups it
emits are still templates: the carrier document keeps its <|injection|> marker and the
assembled injection travels in the objective metadata, because fencing the injection is
the technique's job.

Techniques describe application only. LatentInjectionTechnique has 14 members, one
per separator style from garak's injection_sep_pairs, tagged plain (the injection is
set off by whitespace or quoting) or authority (the delimiter impersonates a system,
admin or legal voice), with ALL / DEFAULT / PLAIN / AUTHORITY aggregates. The nine
carrier families — translation_fr, translation_zh, report, resume, fact_eiffel,
fact_legal, whois, whois_snippet, latent_jailbreak — are seed metadata selected
through a families run parameter, not techniques, so any technique applies to any family.

The scenario assembles the campaign. One AtomicAttack per (technique, family,
trigger), each a standard PromptSendingAttack. Bounding an attack to a single trigger
keeps its success contract unambiguous: its SubStringScorer looks for the one string
that attack's prompts actually asked for. BASELINE_ATTACK_POLICY is Forbidden — the
resolved templates still hold an injection marker, so there is nothing meaningful to send
as a baseline, and the bare technique already covers sending with no fencing at all.

latent_jailbreak gets its own path. It hides a "write something offensive about
<group>" instruction inside a translation request, so there is no fixed string to match.
It is excluded from the default family set and requires an explicit harm_scorer;
selecting it without one raises with a message naming the fix. The check runs before any
prompt is assembled, so a run-size estimate refuses the selection rather than failing
later at scoring time.

Determinism, because resume matches previously executed work by name. Garak thins its
cross products with an unseeded random.sample and assembles its fact-snippet contexts
the same way. Neither is usable here. The cross product is capped per (family, trigger) by
a round-robin walk that advances every axis at once, so the capped population keeps a
spread of tasks, carrier documents and injection templates instead of every variation of
one corner; multi-snippet carrier documents are assembled by a rotating window. The same
inputs always produce the same prompts in the same order, and atomic-attack names are
stable across runs.

Tests and Documentation

Tests — 61 new unit tests, all passing:

• tests/unit/scenario/garak/test_latent_injection.py (39) covers technique expansion and
  the plain/authority partition, snippet assembly, the dataset configuration, atomic-attack
  construction and naming, separator rendering, per-trigger scoring, the missing-harm-scorer
  error, and determinism (identical prompts and names across two runs).
• tests/unit/datasets/test_garak_latent_injection_dataset.py (22) covers the ported
  datasets: required metadata on every seed, marker integrity, and that no garak templating
  marker survives the port.

Rendering is checked against the failure modes that matter here: that every marker is
substituted, that payload-inside-instruction-inside-separator nests in the right order, and
that carrier documents containing literal braces (WHOIS records, JSON fragments) survive
rendering — substitution is str.replace, never str.format.

The full tests/unit suite passes locally, as does pre-commit run over every changed
file (ruff format, ruff check, ty, and the notebook hooks).

Documentation — doc/scanner/garak.py gains a LatentInjection section covering the
techniques, the aggregates, the carrier families, the latent_jailbreak exception and a
CLI example, with doc/scanner/garak.ipynb kept in sync.

On JupyText: the change to doc/scanner/garak.py is markdown cells only — no code cell was
added or altered, and the notebook diff touches a single markdown cell with no changes to
outputs or execution counts. I therefore did not re-run
jupytext --execute --to notebook ./doc/scanner/garak.py, since executing it requires live
target endpoints and would rewrite unrelated outputs. Happy to run it if a maintainer would
rather see it executed.

[microsoft-github-policy-service]

Juhie (@juhiechandra) please read the following Contributor License Agreement(CLA). If you agree with the CLA, please reply with the following information.

@microsoft-github-policy-service agree [company="{your company}"]

Options:

• (default - no company specified) I have sole ownership of intellectual property rights to my Submissions and I am not making Submissions in the course of work for my employer.

@microsoft-github-policy-service agree

• (when company given) I am making Submissions in the course of work for my employer (or my employer has intellectual property rights in my Submissions by contract or applicable law). I have permission from my employer to make Submissions and enter into this Agreement on behalf of my employer. By signing below, the defined term “You” includes me and my employer.

@microsoft-github-policy-service agree company="Microsoft"

Contributor License Agreement

Contribution License Agreement

This Contribution License Agreement (“Agreement”) is agreed to by the party signing below (“You”),
and conveys certain license rights to Microsoft Corporation and its affiliates (“Microsoft”) for Your
contributions to Microsoft open source projects. This Agreement is effective as of the latest signature
date below.

1. Definitions.
   “Code” means the computer software code, whether in human-readable or machine-executable form,
   that is delivered by You to Microsoft under this Agreement.
   “Project” means any of the projects owned or managed by Microsoft and offered under a license
   approved by the Open Source Initiative (www.opensource.org).
   “Submit” is the act of uploading, submitting, transmitting, or distributing code or other content to any
   Project, including but not limited to communication on electronic mailing lists, source code control
   systems, and issue tracking systems that are managed by, or on behalf of, the Project for the purpose of
   discussing and improving that Project, but excluding communication that is conspicuously marked or
   otherwise designated in writing by You as “Not a Submission.”
   “Submission” means the Code and any other copyrightable material Submitted by You, including any
   associated comments and documentation.
2. Your Submission. You must agree to the terms of this Agreement before making a Submission to any
   Project. This Agreement covers any and all Submissions that You, now or in the future (except as
   described in Section 4 below), Submit to any Project.
3. Originality of Work. You represent that each of Your Submissions is entirely Your original work.
   Should You wish to Submit materials that are not Your original work, You may Submit them separately
   to the Project if You (a) retain all copyright and license information that was in the materials as You
   received them, (b) in the description accompanying Your Submission, include the phrase “Submission
   containing materials of a third party:” followed by the names of the third party and any licenses or other
   restrictions of which You are aware, and (c) follow any other instructions in the Project’s written
   guidelines concerning Submissions.
4. Your Employer. References to “employer” in this Agreement include Your employer or anyone else
   for whom You are acting in making Your Submission, e.g. as a contractor, vendor, or agent. If Your
   Submission is made in the course of Your work for an employer or Your employer has intellectual
   property rights in Your Submission by contract or applicable law, You must secure permission from Your
   employer to make the Submission before signing this Agreement. In that case, the term “You” in this
   Agreement will refer to You and the employer collectively. If You change employers in the future and
   desire to Submit additional Submissions for the new employer, then You agree to sign a new Agreement
   and secure permission from the new employer before Submitting those Submissions.
5. Licenses.

• Copyright License. You grant Microsoft, and those who receive the Submission directly or
  indirectly from Microsoft, a perpetual, worldwide, non-exclusive, royalty-free, irrevocable license in the
  Submission to reproduce, prepare derivative works of, publicly display, publicly perform, and distribute
  the Submission and such derivative works, and to sublicense any or all of the foregoing rights to third
  parties.
• Patent License. You grant Microsoft, and those who receive the Submission directly or
  indirectly from Microsoft, a perpetual, worldwide, non-exclusive, royalty-free, irrevocable license under
  Your patent claims that are necessarily infringed by the Submission or the combination of the
  Submission with the Project to which it was Submitted to make, have made, use, offer to sell, sell and
  import or otherwise dispose of the Submission alone or with the Project.
• Other Rights Reserved. Each party reserves all rights not expressly granted in this Agreement.
  No additional licenses or rights whatsoever (including, without limitation, any implied licenses) are
  granted by implication, exhaustion, estoppel or otherwise.

6. Representations and Warranties. You represent that You are legally entitled to grant the above
   licenses. You represent that each of Your Submissions is entirely Your original work (except as You may
   have disclosed under Section 3). You represent that You have secured permission from Your employer to
   make the Submission in cases where Your Submission is made in the course of Your work for Your
   employer or Your employer has intellectual property rights in Your Submission by contract or applicable
   law. If You are signing this Agreement on behalf of Your employer, You represent and warrant that You
   have the necessary authority to bind the listed employer to the obligations contained in this Agreement.
   You are not expected to provide support for Your Submission, unless You choose to do so. UNLESS
   REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING, AND EXCEPT FOR THE WARRANTIES
   EXPRESSLY STATED IN SECTIONS 3, 4, AND 6, THE SUBMISSION PROVIDED UNDER THIS AGREEMENT IS
   PROVIDED WITHOUT WARRANTY OF ANY KIND, INCLUDING, BUT NOT LIMITED TO, ANY WARRANTY OF
   NONINFRINGEMENT, MERCHANTABILITY, OR FITNESS FOR A PARTICULAR PURPOSE.
7. Notice to Microsoft. You agree to notify Microsoft in writing of any facts or circumstances of which
   You later become aware that would make Your representations in this Agreement inaccurate in any
   respect.
8. Information about Submissions. You agree that contributions to Projects and information about
   contributions may be maintained indefinitely and disclosed publicly, including Your name and other
   information that You submit with Your Submission.
9. Governing Law/Jurisdiction. This Agreement is governed by the laws of the State of Washington, and
   the parties consent to exclusive jurisdiction and venue in the federal courts sitting in King County,
   Washington, unless no federal subject matter jurisdiction exists, in which case the parties consent to
   exclusive jurisdiction and venue in the Superior Court of King County, Washington. The parties waive all
   defenses of lack of personal jurisdiction and forum non-conveniens.
10. Entire Agreement/Assignment. This Agreement is the entire agreement between the parties, and
    supersedes any and all prior agreements, understandings or communications, written or oral, between
    the parties relating to the subject matter hereof. This Agreement may be assigned by Microsoft.