Add MAP document and project schema foundation

[rajanbor]

Outcome

Implements the first phase of the schema roadmap:

• JSON Schema draft 2020-12 contracts for typed MAP documents and map.config.json
• human guides, complete examples, and seven invalid fixtures
• dependency-free offline schema validation in CI
• stricter CLI config validation with field paths and safe relative paths
• typed frontmatter metadata exposed by the context compiler
• specVersion: 0.1 in newly initialized workspaces while v2/v3 stay compatible
• schemas attached to pattern releases

Verification

• node library/scripts/validate-schemas.ts
• node library/scripts/build-registry.ts --check
• pnpm lint
• pnpm typecheck
• pnpm test (140 tests)
• pnpm build
• pnpm audit --audit-level=low
• clean map init --yes + map doctor smoke test
• repository map doctor: 0 problems

Closes #95
Closes #89