fix: de-duplicate skill quality rules and resolver overlap

[24601]

Summary

• de-duplicate cross-cutting skill quality rules by referencing skills/conventions/quality.md instead of repeating the same citation/back-link/notability guidance across multiple skills
• tighten resolver disambiguation between maintain and citation-fixer
• remove the "citation audit" trigger from maintain so citation-fixer owns that phrase cleanly

Why this change

gbrain doctor --json was reporting resolver/DRY warnings in the skill layer even though runtime health was otherwise fine.

Before this patch:

• resolver health: warnings
• root cause 1: repeated quality rules pasted into multiple skill files
• root cause 2: overlap between maintain and citation-fixer

After this patch:

• resolver health: ok
• overall gbrain doctor --json: healthy

This keeps the skill layer closer to the architecture the repo already wants:

• shared cross-cutting conventions live in skills/conventions/quality.md
• skill routing stays MECE enough for checkResolvable() / gbrain doctor

Scope

This is intentionally narrow.

No runtime command behavior changed.
No engine/schema/search logic changed.
No version bump or changelog entry included.

The only behavior-level change is trigger ownership:

• citation-fixer keeps "citation audit"
• maintain remains the broader health sweep skill

Files changed

• skills/RESOLVER.md
• skills/ingest/SKILL.md
• skills/enrich/SKILL.md
• skills/setup/SKILL.md
• skills/signal-detector/SKILL.md
• skills/idea-ingest/SKILL.md
• skills/media-ingest/SKILL.md
• skills/meeting-ingestion/SKILL.md
• skills/maintain/SKILL.md

Verification

bun test test/resolver.test.ts test/skills-conformance.test.ts
bun run src/cli.ts doctor --json

Observed results:

• resolver tests: pass
• skill conformance tests: pass
• gbrain doctor --json: healthy
• resolver health: ok

Notes

I kept this as a hygiene-only patch rather than bundling it into a larger docs/skills wave so it is easy to review, merge, or reapply.