feat(engine): materialize deterministic Diff ViewData

[Dencyuman]

Summary

• materialize deterministic added, removed, updated, moved, and moved-and-updated Diff changes from immutable definition snapshots
• validate canonical snapshots, semantic hashes, Project compatibility, state-independent Query inputs, include filters, and explicit LDL move history before comparison
• preserve typed field differences plus before, after, and union source references without heuristic identity matching

Linked Issues

• Closes [Feature]: Materialize Diff ViewData #70

Contributor Agreement

• I have read and agree to the LayerDraw Contributor License Agreement 1.0 and confirm that I have the rights and any employer authorization required to submit this Contribution.

See the Contributor License Agreement and Contributor Privacy Notice.

Scope

• Documentation only
• LDL / schema / protocol
• Engine / Runtime / Query / View
• SDK / MCP / client integration
• Server / storage / realtime / access
• Registry / packs / templates
• Release / governance / legal

Checks

• I did not add secrets, customer data, private deployment config, or local agent config.
• I checked the package boundary and licensing docs for affected paths.
• I updated generated artifacts or fixtures if a schema changed.
• I documented any public API, protocol, license, or release impact.
• I identified compatibility or migration impact, or confirmed there is none.
• I identified whether a release note is required.

Contract Impact

• Affected components and delivery bundles: Go Engine in-process Diff ViewData materialization only.
• LDL / schema / protocol / container impact: No language, schema, protocol, or container change. Protocol generation remains deferred to [Feature]: Expose complete ViewData through Engine Protocol #71.
• State or data migration impact: None; Diff remains state-independent.
• License or dependency impact: None.
• Release note: Not required before the complete ViewData milestone is released.

Validation

• full Go race test, TypeScript test, lint, typecheck, conformance, integration, security, license, and packaged binary gates
• Engine package coverage: 88.0% (required 88.0%)
• Patch coverage: 87.1% (required 80.0%)
• deterministic Engine WASM artifact verification and packaged WASM test from the clean committed tree