Release RC.3 tooling support

[ObjectIsAdvantag]

Summary

• add immutable MCP Description 0.8.0-rc.3 validator support and frozen fixtures
• add RC.3 core projection, merge, selection, migration, and component-reference resolution
• enable RC.2 and RC.3 component-reference resolution with terminal-target provenance
• simplify snapshot provenance around package-owned integrity and informational upstream Git metadata
• prepare @mcpdesc/validator 0.10.0 and @mcpdesc/core 0.9.0

Snapshot integrity

• record maintainer-approved additive tooling-metadata corrections for RC.2 and RC.3 component-reference provenance
• leave schemas, conformance results, diagnostics, and frozen fixtures unchanged

Validation

• npm run check
• 660 validator tests
• validator declarations and strict-CSP/browser bundles
• validator and core package-content checks
• isolated JavaScript and TypeScript consumer checks
• dry-run tarballs for validator 0.10.0 and core 0.9.0
• git diff --check

Release order

1. Publish and verify @mcpdesc/validator@0.10.0 from validator-v0.10.0.
2. Re-run core readiness against the published validator.
3. Publish and verify @mcpdesc/core@0.9.0 from v0.9.0.

AI assistance

GitHub Copilot assisted with implementation, tests, documentation, release preparation, and validation. The maintainer reviewed the behavior and remains accountable for the result.