feat: add deterministic hybrid retrieval core

[Odenknight]

Summary

• publish the Full-owned gkos-retrieval/1.0.0-draft.1 contract and exact cross-language fixtures
• add deterministic heading chunking, SQLite FTS5 generations, typed filters, RRF/MMR, parent expansion, confidence, exact citations, and provider-neutral vector/rerank interfaces
• add the additive gkx search command while preserving legacy CLI, REST, Graphiti, and Navigation behavior
• enforce trusted configuration, source-record-atomic policy, immutable derived stores, strict envelope validation, and credential-safe provider adapters

Verification

• npm test: 302 passed
• npm run test:navigation: 44 passed
• npm run test:intelligence: 4 passed
• typecheck, build, nomenclature, license, and pack checks passed
• Lite copied all nine contract files byte-for-byte and passed Rust cross-language conformance locally
• reciprocal Full/Lite review approved with no remaining high, medium, or blocking findings

Boundaries

• no source-note writes
• no temporal as_of mapping until the current Standard mapping is owner-ratified in Phase 2
• no merge, release, deployment, or provider provisioning in this PR

September 14, 2026 disposition

Closed as already integrated. Exact PR head 0164f3d5b2c698cbf048c8e0e53323def80eb251 is an ancestor of main 91433b158b4b9bc30bd4d43b7dd8f61363647960, verified with git merge-base --is-ancestor. No additional merge or feature admission is needed. Evidence branches are retained; this closure grants no release or runtime authority.

Exact disposition ledger.