perf(contributor-growth): trim sentiment skill routing metadata

[Kaap10]

Summary

• Trims the always-on frontmatter (description and when_to_use) for sentiment following the Optimize skill token cost across all families (setup-family recipe) #1342 recipe.
• Drops always-on frontmatter estimate from ~241 tokens down to ~131 tokens ($\le 200$ budget) by removing prose duplication.
• Preserves all five quoted routing trigger phrases, RFC-AI-0004 gate evidence references, and baseline fallback rules verbatim; skill body (lines 34+) is completely untouched.
• Syncs the magpie-contributor-growth published always-on estimate in docs/setup/marketplace.md to ~0.7k.

Type of change

• Skill change (.claude/skills/<name>/) — eval fixtures updated below
• Tool / bridge contract (tools/<system>/*.md)
• Python package (tools/*/ with pyproject.toml)
• Groovy reference impl
• Cross-cutting (RFC, AGENTS.md, sandbox, privacy-LLM)
• Documentation (docs/, README.md, CONTRIBUTING.md)
• Project template (projects/_template/)
• CI / dev loop (prek, workflows, validators)
• Other:

Test plan

• prek run --all-files passes
• For skill changes: eval suite passes for the affected skill (tools/skill-evals/evals/contributor-sentiment/)
• Token count verification: measured_tokens stamped to 4627 (down from 4720); always-on frontmatter estimated at 131.0 tokens ($524 \text{ chars} \div 4 \le 200$).
• Invariant audit: surface_hash (sha256:c325db1d99634a51), all #–#### headings, and **Golden rule N — ...** headlines verified 100% byte-identical.
• Marketplace sync: docs/setup/marketplace.md table estimate verified in sync with live frontmatter (~0.7k).

RFC-AI-0004 compliance

• HITL — any new mutation is gated on explicit user confirmation
• Vendor neutrality — placeholders (<PROJECT>, <tracker>, <upstream>, <security-list>) used in all skill / tool prose
• Write-access discipline — no autonomous outbound messages; drafts only, sent on confirmation

Linked issues

Part of #1348 (Phase 1, PR 2) — Refs #1342

Notes for reviewers (optional)

Scoped strictly to sentiment following the one-skill-at-a-time recipe. PR 1 covers onboarding-concierge (#1481) and PR 3 will cover activity-sweep.

[Kaap10]

Ready for review!
Trimmed sentiment always-on frontmatter from ~241 to ~131 tokens (comfortably under the 200 budget)

[onlyarnav]

lgtm