docs: bring the README up to date with the last five releases

The README had fallen behind v2.3.0-v2.7.0, and parts of it were not
true. Checked every claim against the code and BENCHMARKS.md:

- Three of the six Quick Start snippets no longer compiled (Agent
  Memory, Consolidation, OpenClaw); all six now do.
- Hybrid search was described as RRF throughout. The default has been
  weighted 0.4/0.6 fusion since v2.5.0; re-ranking and confidence
  rejection run only in the OpenClaw backend.
- The `float16` feature does not halve embedding storage (the store
  always writes f32), `--features agent` enables nothing, "Source
  Isolation" is not wired in, and nothing backs "billion-scale" IVF-PQ.
- "Cryptographically verifiable" overstated an unkeyed, session-scoped
  FNV-1a ledger; "Zero C dependencies" was false while zlib-ng was the
  default deflate backend.
- Stale numbers: tests (1,650 -> 1,868), Rust badge (1.75 is below
  edition 2024's floor), 6.5 KB/record on disk (BENCHMARKS.md: 1.7 KB),
  consolidation and hybrid-search latency, and a feature-flag table
  broken by a paragraph pasted into it.
- The file schema, module table and crate map now match the code.

Adds a "What's new (v2.2 -> v2.7)" section for collaborators, leading
with the silent Extensible Array read bug fixed in v2.7.0. Footer links
point at git.redclaw.dev. CLAUDE.md: clawhdf5-migrate is the SQLite
migration tool, and MemoryConfig::compression is off by default.

Co-Authored-By: Claude Opus 5.5 (1M context) <[email protected]>

docs/QUICKSTART.md

@@ -567,4 +567,4 @@ let final_results = confidence::reject_low_confidence(
 
 ---
 
-<p align="center"><em>Built by <a href="https://github.com/redclawsystems">RedClaw Systems</a></em></p>
+<p align="center"><em>Built by <a href="https://git.redclaw.dev/quantumclaw">RedClaw Systems</a></em></p>

docs/USE_CASES.md

@@ -232,4 +232,4 @@ clawhdf5-agent = { version = "2.0", features = ["agent", "float16", "accelerate"
 
 ---
 
-<p align="center"><em>Built by <a href="https://github.com/redclawsystems">RedClaw Systems</a></em></p>
+<p align="center"><em>Built by <a href="https://git.redclaw.dev/quantumclaw">RedClaw Systems</a></em></p>