phase2-onboarding: adopt Phase 0 contract for tree-sitter-m-vscode

[rafael5]

Summary

Tier-3 onboarding per AI-discoverability-plan.md §3.4 and phase1-plan.md §9. Third and final tier-3 repo to ship the Phase-0 contract — completes Phase 2 onboarding after m-modern-corpus PR #2, tree-sitter-m PR #4, and m-test-engine PR #2.

What landed

Surface	Contents
AGENTS.md	Renamed from CLAUDE.md (existing 68-line content preserved verbatim above); CLAUDE.md now a symlink to AGENTS.md. Five Phase-0 sections appended (Setup / Test / Build / Verify / Guardrails).
dist/repo.meta.json	Phase-0 contract. Exposes extension_info (dist/extension-info.json) + package_json + language_configuration. Consumes tool:tree-sitter-m and tool:m-cli. License MIT.
dist/extension-info.json	Hand-authored, deterministic distillation of package.json contributes.*: 4 commands, 4 settings (m-cli.enabled / path / args / trace.server), 1 language (m with .m / .mac / .int extensions), 1 grammar (source.m → syntaxes/m.tmLanguage.json), marketplace id rafael5.tree-sitter-m-vscode. Sorted keys, 2-space indent.
tools/check-manifest.py	Stdlib-only validator — copied verbatim from tree-sitter-m, same pattern as m-test-engine.
Makefile	First Makefile for this repo. Three targets: manifest (informational no-op — extension-info.json is hand-authored), check-manifest, check-docs-prose.
.github/workflows/ci.yml	First CI workflow for this repo. Phase-0 gates (check-manifest, check-docs-prose) run before npm ci / npm run lint / npm run compile, so a broken manifest fails fast without spinning up Node.

Verification (all green)

• make manifest — informational pointer
• make check-manifest — manifest valid + all 3 exposes.* paths present
• make check-docs-prose — docs/ (lsp-setup.md) is prose-only
• Canonical Track-A validator (.github/profile/build/validate-repo-meta.py) — OK: dist/repo.meta.json

Design notes

• Hand-authored extension-info.json (not generated). package.json contributes.* already exists; a generator would be a parse + transform with no real degrees of freedom. AGENTS.md § Guardrails captures the "mirror the change into extension-info.json in the same commit" rule for reviewer enforcement.
• dist/ is already tracked. This repo's .gitignore deliberately omits the dist/ ignore (the comment notes the .wasm grammar is committed so users can clone-and-package without docker). The gitignore bug that bit tree-sitter-m's ade59d6 didn't recur here — no exception was needed.
• Manifest gate before npm ci. Cheaper to fail in 100ms on malformed JSON than to wait for npm install + tsc. The CI ordering reflects this.

Phase 2 progress: 3 of 3 tier-3 repos onboarded with this PR.

Repo	Status
m-modern-corpus	Onboarded
tree-sitter-m	Onboarded
m-test-engine	Onboarded
tree-sitter-m-vscode	This PR

Phase 1 hook

Once .github ships build-catalog.py (Phase-1 Track B) and adds tree-sitter-m-vscode to its tier-3 list, this repo's manifest will be picked up by the org catalog automatically — completing the parent plan's Phase 2 exit criterion ("all tier-3 repos appear in generated tools.json with verified_on dates within 30 days").

Test plan

• All local gates green
• Canonical Track-A validator green
• CI green on this PR (manifest + docs-prose gates run before npm install, then npm ci + npm run lint + npm run compile)