[bugfix] Anchor .moderne ignore pattern so it applies at any depth

[duncdrum]

Summary

• .moderne/* (slash in the middle) is anchored to the repo root by gitignore's rules, so it only ignored the top-level .moderne/ directory. Nested .moderne/ directories created when running Moderne recipes scoped to a submodule (e.g. exist-core/.moderne/) were left untracked, showing up as a dirty checkout.
• Switches the pattern to **/.moderne/* so it applies at any depth, and anchors the context//moderne.yml negations to the repo root (!/.moderne/context/, !/.moderne/moderne.yml) so nested .moderne dirs elsewhere stay fully ignored while the root's committed context files remain tracked.

What Changed

• .gitignore: .moderne/* → **/.moderne/*, negations anchored with a leading /.

Closes #6590

Test Plan

• git check-ignore -v exist-core/.moderne/apply → now ignored
• git check-ignore -v .moderne/context/architecture.md → still tracked (not ignored)
• git status no longer reports nested .moderne working directories as dirty

[github-actions]

📊 XQTS result comparison

Comparison of this run against develop.

Warning

20 test cases were recorded in only one of the two runs (0 only in the previous run, 20 only in the current run). The runner's JUnit output is not fully deterministic (see eXist-db/exist-xqts-runner#74), so totals and per-category deltas include recording noise; the newly passing/failing lists count only tests recorded in both runs.

Metric	develop	this run	Change
🟢 Passed	28,828 (90.67%)	28,845 (90.66%)	+17 (-0.00 pp)
🔴 Failures	1,566	1,569	+3
➖ Errors	134	134	0
➖ Skipped	1,267	1,267	0
🧪 Total tests	31,795	31,815	+20

Relative to develop: 0 newly passing, 2 newly failing, 0 new errors, 0 newly skipped — counting only tests recorded in both runs whose outcome changed.

🔴 Newly failing tests (2)

• Constr-inscope-2 (was passing)
• Constr-inscope-3 (was passing)

⚪ Recorded only in this run (20)

• raytracer (failing)
• sgml-queries-results-q3 (passing)
• functx-fn-nilled-all (passing)
• functx-fn-replace-5 (passing)
• functx-fn-normalize-space-9 (passing)
• functx-fn-string-2 (passing)
• functx-fn-not-5 (passing)
• functx-fn-normalize-space-1 (passing)
• functx-fn-starts-with-8 (passing)
• functx-fn-number-all (passing)
• functx-fn-replace-18 (passing)
• K2-DirectConOther-51 (passing)
• fo-test-fn-max-003 (passing)
• fo-test-fn-min-004 (passing)
• fo-test-fn-tail-003 (passing)
• fo-test-fn-remove-004 (passing)
• fo-test-map-find-001 (passing)
• fo-test-fn-deep-equal-003 (passing)
• fo-test-fn-count-004 (passing)
• fo-test-fn-fold-left-005 (passing)

_{Runtime: 341.8s (+70.45s vs develop).}