feat: consolidate TraceDecay V2 PR8-PR13 delivery

[ScriptedAlchemy]

Summary

This draft PR is the consolidated delivery branch for TraceDecay V2 PR8 through PR13.

• PR8: completed session/LCM temporal retrieval authority.
• PR9/PR10: code intelligence, exact/lexical/graph retrieval, FastEmbed semantic projection, calibration, and byte-stable fallback.
• PR11: application, policy, configuration, catalog, Git transaction, and feedback-cycle core.
• PR12: CLI/MCP/HTTP/LSP production bindings and canonical diagnostics/impact readers.
• PR13: Hook V2, Context Scout, host lifecycle/bundles, read-only GitHub/CI feedback, and agent proximity.

The branch also contains the supporting rusqlite runtime cutover, worktree-aware incremental indexing, storage retention/Doctor integration, and direct product tests required by the canonical V2 plans.

Verification

• Focused PR8-PR13 product tests
• cargo check --all-features
• cargo test --all-features
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo fmt --all -- --check
• Dashboard and host integration checks
• Distribution/FastEmbed acceptance
• Linux, macOS, and Windows CI

Current status: implementation is still being consolidated from the shared checkout and CI is red. This PR remains draft until the working tree is committed, broad verification is stable, and the historical conventional-commit blocker is resolved. It must not be merged in its current state.

Safety boundaries

GitHub review ingestion is read-only. Semantic indexing never blocks exact/lexical/graph retrieval and publishes only complete compatible generations. Local coordination logs, private transcript evidence, secrets, and ad hoc artifacts are excluded from commits.