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]>

conformance/README.md

@@ -10,9 +10,11 @@ conformance/run.sh --no-fetch                                    # use the cache
 conformance/run.sh --update-baseline                             # after an intended change in results
 ```
 
-Latest result (tank, 2026-09-27, `conformance/run.sh --no-fetch`): 602 of
-697 files ok, 0 our-error, 0 mismatch, 3 ref-bug, 92 h5py-cannot-read, and
-no panic, hang, crash or out-of-memory. The report with every file is
+Latest result (tank, 2026-09-28 04:29 UTC, `conformance/run.sh --no-fetch
+--update-baseline`): 602 of 697 files ok, 1 our-error, 0 mismatch, 2
+ref-bug, 92 h5py-cannot-read, and no panic, hang, crash or out-of-memory.
+The our-error file is `bad_nbit_parms_walk.h5`, which flips between ref-bug
+and our-error from run to run (see `docs/known-issues.md`). The report with every file is
 [`CONFORMANCE.md`](../CONFORMANCE.md).
 
 ## Classes
@@ -32,8 +34,8 @@ Where h5py itself returns wrong values through a known h5py bug (the
 big-endian variable-length bug: elements returned with the file's bytes
 under a little-endian dtype), `ref.py` checks that the installed h5py has
 the bug, corrects the values before hashing and marks them `ref_fix`, so
-those objects are still compared. The evidence for the three current
-ref-bug files is under "Conformance: the last non-ok files" in
+those objects are still compared. The evidence for the three remaining
+non-ok files (ref-bug or, for one, our-error) is under "Conformance: the last non-ok files" in
 [`docs/known-issues.md`](../docs/known-issues.md).
 
 Needs Rust, `git`, `h5dump` (Debian/Ubuntu `hdf5-tools`), `libaec` (for the