docs: withdraw the ZeroClaw integration claims

CLAUDE.md said ZeroClaw "imports this as a Cargo feature (clawhdf5
feature flag)" and uses clawhdf5 as its memory backend; the agent crate
called itself the "ZeroClaw agent memory HDF5 backend"; the migrator
claimed to read "the ZeroClaw layout". Checked on 2026-09-25 against
ZeroClaw v0.8.5 (its latest release), the osobh/zeroclaw fork (on
v0.8.5) and both histories back to February 2026:

- no `clawhdf5` feature, dependency or memory backend has ever existed
  in ZeroClaw; its backends are sqlite, lucid, postgres, qdrant,
  markdown and none, behind its own `Memory` trait;
- ZeroClaw's SQLite schema is a single `memories` table (id, key,
  content, category, embedding, created_at, updated_at); the
  migrator's memory_chunks/sessions/entities/relations layout never
  existed in ZeroClaw, so it cannot read a ZeroClaw database.

Decision: withdraw the claims (as with OpenClaw); clawhdf5 is a
standalone library with no framework integration. The migrator's
default layout is documented as its own. ZEROCLAW_VERSION keeps its name
and value (it is the persisted `edgehdf5_version` writer tag) with a
doc comment saying it is unrelated to ZeroClaw.

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

CHANGELOG.md

@@ -3,6 +3,14 @@
 ## Unreleased
 
 ### Upgrade Notes
+- **ZeroClaw does not use clawhdf5.** The project described itself as
+  ZeroClaw's memory backend ("imported as a `clawhdf5` Cargo feature"). Checked
+  against ZeroClaw v0.8.5 (the latest release), the `osobh/zeroclaw` fork and
+  their full history: no such feature or backend has ever existed. And
+  `clawhdf5-migrate`'s "ZeroClaw layout" (`memory_chunks`, `sessions`,
+  `entities`, `relations`) is not ZeroClaw's schema — ZeroClaw uses a single
+  `memories` table — so the migrator cannot read a ZeroClaw database. The
+  claims are withdrawn; the migrator's layout is documented as its own.
 - **OpenClaw is not supported, and never was.** The docs described a
   "drop-in" OpenClaw memory backend enabled with `memory.backend = "clawhdf5"`.
   That config was never valid in any OpenClaw release (v2026.2–v2026.7