poly-kv 0.1.0-alpha.3

Shared compressed KV-cache pool for multi-agent context. Two-tier codec policy (fib-quant cold + turbo-quant hot) with typed receipts.
Documentation
# Expected Final File Tree

```text
<repo>/
  Cargo.toml
  AGENTS.md
  README.md
  crates/
    quant-codec-core/
      Cargo.toml
      src/
        lib.rs
        ids.rs
        digest.rs
        dtype.rs
        shape.rs
        codec.rs
        eval.rs
        error.rs
      tests/
        shape_validation.rs
        serde_roundtrip.rs
        digest_stability.rs
    poly-kv/
      Cargo.toml
      README.md
      src/
        lib.rs
        error.rs
        manifest.rs
        receipts.rs
        pool.rs
        reader.rs
        memory.rs
        metrics.rs
        codecs/
          mod.rs
          raw_exact.rs
          q8_keys.rs
          value.rs
        adapters/
          mod.rs
          turbo_quant.rs
          fibquant.rs
      tests/
        synthetic_roundtrip.rs
        memory_accounting.rs
        shape_rejection.rs
        receipt_roundtrip.rs
        deterministic_replay.rs
      benches/
        synthetic_pool.rs
  docs/
    SOURCE_OF_TRUTH_MAP.md
    POLY_KV_SCHEMA_PROPOSAL.json
    PUBLIC_CLAIM_BOUNDARY.md
    BENCHMARK_PLAN.md
  scripts/
    preflight.sh
    run_rust_gates.sh
    validate_schemas.py
    check_public_claims.py
    validate_final_state.py
  .codex-runs/
    <run-id>/
      ...
```