feat(hooks): add hybrid HOOK.json manifest support

[ksamaschke]

Summary

• add hybrid hook metadata support with HOOK.json as authoritative machine manifest and HOOK.md as human-facing fallback
• enforce hook target compatibility at install/sync time (skip incompatible hooks with warning)
• keep CLI helper exports import-safe for tests (require.main === module) and retain serve helper test coverage

Changes

• update hook catalog parsing to prefer HOOK.json, parse compatible targets and registrations, and keep HOOK.md fallback
• update hook executor to skip incompatible target installs with HOOK_TARGET_INCOMPATIBLE
• add installer tests for JSON metadata ingestion and target compatibility behavior
• update hook docs for hybrid manifest guidance

Test Plan

• npm run build:quick
• node --test dist/tests/installer/*.test.js

[ksamaschke]

ICA-REVIEW-RECEIPT
Reviewer-Stage: 3 (temp checkout)
Reviewer-Agent: codex (subagent)
Head-SHA: 92e6b19
Findings: 0
NO FINDINGS
Result: PASS

Validation:

• npm run build:quick
• node --test dist/tests/installer/*.test.js