Add release notes and an upgrade guide to the docs

[ckelseynv]

Description

Adds two pages to the public docs: Release Notes, starting with 1.0.0, and an Upgrade Guide for updating from a version before 1.0.0. People who read the docs rather than GitHub had no release notes to look at.

The 1.0.0 notes are adapted from the release notes master doc. The Upgrade Guide starts from the fact that most machines need nothing extra, then covers the few setups that need a small step:

• tidying up the old PAIR.app on macOS;
• an LM Studio that an earlier PAIR installed;
• browser clients affected by the CORS change.

Changelog title

n/a

Changelog body

n/a

Bumps

• services: none
• nvpair-cluster-manager: none
• nvpair-engine-manager: none
• nvpair-errors: none
• nvpair-job-scheduler: none
• nvpair-manual-nodes: none
• nvpair-node-info: none
• nvpair-node-scanner: none
• nvpair-node-settings: none
• nvpair-proxy: none
• nvpair-tui: none
• nvpair-ui-broker: none
• nvpair-workload-manager: none

Scope

• docs/release-notes.mdx (new): the 1.0.0 notes, covering what's new, compatibility notes, targeted bug fixes, community contributions with PR links, and special thanks. Notes before 1.0.0 are linked on GitHub Releases.
• docs/upgrade-guide.mdx (new). It opens by saying an update keeps settings, cluster membership, and models, and that every machine in a cluster should run the same version. Each section then says who it applies to:
  • On macOS, tidy up the old app: run the old app's uninstall-macos.sh without --purge, then install NVIDIA PAIR.app. 0.1.0 and 0.1.1 both ship that script, and both keep data without --purge.
  • If an earlier PAIR installed LM Studio for you: it keeps working, but it has no install marker (installed-by-pair.json), so Uninstall, Reset app data, and uninstalling PAIR leave it. Steps to remove it while keeping models, or to reinstall it so PAIR manages it.
  • If you use PAIR from a web page or browser extension: which launch option allows a site for each engine.
  • Checking everything is working.
• fern/docs.yml: both pages under Guides, after Getting Started.
• README.md, docs/getting-started.mdx ("Keeping PAIR Up to Date" and "Learn More"), and docs/known-issues.mdx: link to the new pages. known-issues gains an entry for the LM Studio limitation.

Validation

• Each upgrade step was checked against the code: desktop/scripts/build/macos/uninstall.sh at HEAD, v0.1.0, and v0.1.1; services/nvpair-engine-manager/install.go and provenance.go; manifests/lmstudio.json; desktop/docs/macos-privileged-helper.md; and docs/engine-settings.mdx for the CORS controls.
• Contributor PRs Add Anthropic Messages API Routing #27, fix(ui): show every GPU on a node card, not just the first #34, Fix HTTP connection reuse in engine health probes #37, fix(cluster-manager): announce only persisted endorsement changes #62, Fix workload broadcast ordering and record dedup keys only after successful emit #80, test(services): isolate test app-data state #95, Use the services key in the pair-github-pr release-intent examples #120, Retry failed scheduler priority notifications #122, and Name develop as the branch base in AGENTS.md and CONTRIBUTING.md #126 were checked for merge state and author.
• node scripts/spdx-headers.mjs
• python3 scripts/release-intent/validate_pr.py --description-file <this description> --skip-owned-files-check

Risk

Documentation only. No code, build, or versioned file changes.

Left for the product owner to confirm against the master doc:

• The app is named NVIDIA PAIR (NVIDIA PAIR.app).
• The macOS note does not say models could be lost, because models never live inside the app.
• The bug-fix line names LM Studio only, because llama.cpp never shipped publicly.
• README.md and known-issues.mdx still call Windows on ARM experimental, beside the RTX Spark validation note.

Checklist

• I have read the Contributing Guidelines.
• Every commit is signed off (git commit -s), certifying the Developer Certificate of Origin.
• New or existing tests cover the change. (Documentation only.)
• Relevant documentation is updated.
• I checked the diff, changed filenames, and commit messages for credentials, private data, internal URLs, internal issue identifiers, and generated artifacts.
• I recorded the validation commands and results above.
• I declared version bumps in the release-intent block above. services/versions.json is written by automation — do not edit it by hand.