[GATE-P0-2] Add Tree-sitter PC-6 evidence

[sorted-ai-bot]

Summary

• Add a real Tree-sitter-backed editor parse/classification API for the 10 PC-6 languages.
• Bundle the 10 grammar submodules and wire them into xmake as a static grammar library.
• Add deterministic PC-6 fixtures, test_treesitter, and CI build/run coverage.

Verification

• xmake build -v traveler
• xmake run test_treesitter (50 PASS / 0 FAIL)
• xmake test -v (19/19 targets PASS)
• bash scripts/license_audit.sh

Scope Boundaries

• This PR is PC-6 evidence only.
• This is not a GATE-P0-2 PASS claim.
• No PmoQa formal scoring is requested in this PR.

[github-actions]

PR Auto-Review

AI inference did not produce a response (outcome=failure).
This does not block merge; human review remains authoritative.

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• Model: openai/gpt-4o-mini via actions/ai-inference@v2
• Diff: 50767 bytes (truncated=false)
• Run: https://github.com/YumaKakuya/traveler/actions/runs/25704663415

AI-generated sanity check. CEO remains final merge authority.

[sorted-ai-bot]

@YumaKakuya PR #17 is ready for CEO review/merge decision. Scope: P0-2 PC-6 Tree-sitter evidence only; no GATE-P0-2 PASS claim and no PmoQa formal scoring request.