docs: fact-check the refreshed documentation against its sources

Numbers, API names, feature defaults and PR references checked against
CONFORMANCE.md, BENCHMARKS.md, CHANGELOG.md, the code and git history.

- int8 index figures (1.74x memory, 1.63x QPS) carry the dates git gives
  them (2026-09-19/20, machine not recorded, not re-run) instead of none;
  the Pi 5 1.18x carries 2026-09-21.
- BENCHMARKS headline: the libhdf5 chunked-write figure is the newest
  measurement (35x, 2026-09-23), not 45.3x (2026-08-03).
- Conformance counts follow the 2026-09-28 run (1 our-error, 2 ref-bug)
  in conformance/README.md, ROADMAP.md and CLAUDE.md, with a pointer to
  the bad_nbit_parms_walk.h5 flip.
- README: LZ4 is opt-in; the browser refuses reference/opaque/bitfield/
  time datasets too; zlib-rs byte-identity scoped to what was measured;
  macOS default links the system libz for inflate.
- Crate READMEs: system-zlib-decompress does something (macOS), SweepDetector
  lives in prefetch, checkpoint after more than 500 WAL entries, NetCDF-4
  unlimited-dimension size warning.
- agent-memory.md: string-dataset compression threshold, agents-md prints
  Markdown, float16 file sizes linked to their study.
- known-issues.md: contiguous selection reads, 1.21x vs h5py threads.
- docs/README.md, USE_CASES.md, ROADMAP.md, CLAUDE.md: range-read
  milestones M0-M5 and PRs #17-#19, missing README rows, CLI keygen/verify,
  dated figures, fast-math is not BLAS.

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

crates/clawhdf5-format/README.md

@@ -77,7 +77,7 @@ assert!(!hdr.messages.is_empty());
 | `checksum` | yes | verify Jenkins lookup3 checksums | no |
 | `deflate` | yes | deflate through flate2 | no |
 | `zlib-rs` | yes | flate2's pure-Rust zlib-rs backend, with `runtime_detection` (without it zlib-rs loses SIMD and inflates 3.5x slower) | no |
-| `system-zlib-decompress` | yes | no effect (nothing reads it; kept so existing feature lists still build) | no |
+| `system-zlib-decompress` | yes | macOS only: inflate with the system libz first, falling back to flate2; no effect elsewhere | no (links the system libz on macOS) |
 | `provenance` | yes | SHA-256 provenance hashes | no |
 | `lzf` | yes | LZF (32000) | no |
 | `parallel` | no | rayon-parallel chunk decoding | no |