refactor(hooks)!: gate evolution hooks behind evolution.enabled + delete phantom evolution-quality-gate (P2.3)

[klpanagi]

Summary

P2.3 evolution gating (plan: .matrixx/plans/p2.3-evolution-gating.md, 5 tasks / 3 waves). Two changes:

1. Registration gating — evolution-watcher, evolution-compressor, evolution-hitl now only register when evolution.enabled: true (default false = zero per-tool-call overhead). Previously they registered on every session and invoked handlers on every tool call / message transform, early-returning inside. In-handler config?.enabled checks kept as defense-in-depth.
2. Phantom fix — evolution-quality-gate was never a hook (pure passesQualityGate() fn, no factory, no registration). Removed from HookNameSchema 61→60 with no shim (P2.1 ghost precedent). Pure function, barrel re-export, and pipeline usage kept.

BREAKING CHANGE

disabled_hooks containing "evolution-quality-gate" now fails Zod validation with an actionable enum error (the name never had any effect). Real quality-gate lint hook is untouched (schema, factory, bench, tool-execute wiring).

What changed (6 files, +13/-8)

• src/config/schema/hooks.ts — 1 line deleted (61→60)
• src/plugin/hooks/create-continuation-hooks.ts — const evolutionEnabled = pluginConfig.evolution?.enabled === true, gates compressor + hitl
• src/plugin/hooks/create-tool-guard-hooks.ts — same const, gates watcher
• docs/configurations.md — hook count 60, gating + BREAKING notes
• docs/evolution.md — gating note, quality gate clarified as pure function
• assets/matrixx.schema.json — regenerated via bun run build:schema (60 enum values)

Kept as-is: features/evolution/ (~600 LOC), /evolution command, docs/evolution.md body, evolution tests, real quality-gate hook.

Verification

• bun run typecheck → exit 0; bun run lint → 959 files clean; bun run build → success + schema regen
• bun test tests/features/evolution/ → 23 pass, 0 fail
• rg "evolution-quality-gate" src/ tests/ (quoted) → no matches; passesQualityGate still in barrel + pipeline
• HookNameSchema.safeParse('evolution-watcher') → true; ('evolution-quality-gate') → false with enum error; ('quality-gate') → true
• All edited source files ≤200 LOC (75/164/184)

Checklist

• Targets dev (never master), merge commit only
• Branch refactor/p2.3-evolution-gating, Bun 1.4.0
• No as any / @ts-ignore, no src/index.ts exports, no todo-continuation-enforcer touch
• Rollback: revert merge commit, restore schema entry, build:schema (see plan §Rollback)