feat: enforce Pattern Schema v1

[rajanbor]

Outcome

Adds the first enforced contract for MAP patterns and anti-patterns while validating all existing published content unchanged.

Changes

• add strict Pattern Schema v1 with stable slash-form IDs, lifecycle, MAP Score, evidence, and typed relationships
• retain legacy related as an explicit compatibility field
• add complete pattern and anti-pattern examples plus four invalid fixtures
• validate every repository pattern.yaml, directory identity, required files, duplicate IDs, and relationship targets
• teach the dependency-free YAML reader folded and literal block strings used by pattern metadata
• update human schema and pattern-contract documentation

Verification

• node library/scripts/validate-schemas.ts (4 contracts)
• node library/scripts/build-registry.ts --check (96 patterns)
• pnpm lint
• pnpm typecheck
• pnpm test (141 tests)

Part of #103.