feat(engine): materialize deterministic LDL outputs

[Dencyuman]

Summary

• Materialize deterministic Project and Pack normalized artifacts from typed LDL compiler stages.
• Generate canonical JSON, semantic hashes, validated asset records, SourceMap, SemanticIndex, and SearchDocuments.
• Enforce normative subject kinds, exact Pack manifest provenance, deterministic ordering, and transactional rejection.
• Add regression, golden, permutation, race, and coverage tests.

Validation

• NODE_VERSION=24.18.0 /Users/dencyu/.nvm/nvm-exec make ci
• Overall coverage: 95.7%
• Patch coverage: 95.4%
• Materialize: 95.1%
• Index: 96.3%

Closes #17

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