docs: withdraw the OpenClaw integration claims

The docs described a "drop-in" OpenClaw memory backend enabled with
`memory.backend = "clawhdf5"`. Checked against OpenClaw's source and
docs (v2026.2.26 through v2026.9.6): that config was never valid —
v2026.2-v2026.7 accepted only "builtin"/"qmd" and rejected unknown
keys, so a Gateway given it refuses to start, and v2026.8.1 (OpenClaw
2.0) removed the key. No plugin was ever built (no manifest, no
registration, no tools), nothing was tested against OpenClaw, the
linked github.com/redclawsystems/openclaw is a 404, and
@redclaw/clawhdf5 was never published.

Decision (2026-09-25): not pursuing an OpenClaw plugin for now; ZeroClaw
is the integration target.

- Remove openclaw-integration.md, openclaw-config.md and
  migration-guide.md; add docs/openclaw.md: the status, what a memory
  plugin needs against v2026.9.6 (plugins.slots.memory, manifest with
  kind "memory", registerMemoryCapability / MemorySearchManager,
  prebuilt native packages), and what this repo has as building blocks.
- README, QUICKSTART, USE_CASES, ROADMAP (Track 7 withdrawn), CLAUDE.md
  and the `openclaw` module docs describe ClawhdfBackend as what it is:
  a Markdown-oriented library backend, not an OpenClaw plugin. The
  QUICKSTART example is corrected (the old one called a three-argument
  create that does not exist) and states its limits.
- packages/clawhdf5-node: marked unpublished and broken, "private": true
  so it cannot be published by accident; its bugs (snake_case vs
  camelCase fields, wrong addon path, no way to store an embedding,
  wrong WAL name) are recorded in docs/known-issues.md.
- Two broken rustdoc links fixed along the way.

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

docs/known-issues.md

@@ -279,3 +279,26 @@ the same agent-store interop test.
 
 **Fix:** an empty contiguous dataset gets the undefined address (all `0xff`),
 which is what libhdf5 itself writes.
+
+## The Node.js package (`packages/clawhdf5-node`) does not work
+
+**Status:** open (found 2026-09-25). Unpublished; not built or tested in CI.
+
+The TypeScript wrapper over `crates/clawhdf5-napi` has never run successfully:
+
+- napi-rs converts `#[napi(object)]` fields to camelCase, but the wrapper reads
+  snake_case (`r.line_range`, `s.total_records`, `s.working_count`, …), so
+  every stats and consolidation field comes back `undefined`
+  (`src/index.ts:76-120`).
+- It loads `../clawhdf5.node`, but `napi build --platform` produces
+  `clawhdf5.<triple>.node`; `main` points at `index.js` while `tsc` writes to
+  `dist/`; `napi prepublish` expects per-platform packages that are not
+  defined.
+- `save`/`saveBatch` exist in the napi layer but not in the wrapper, so a
+  TypeScript caller cannot store an embedding at all.
+- The WAL for `agent.brain` is `agent.h5.wal` (the store uses
+  `with_extension("h5.wal")`), not `agent.brain.wal` as the old docs and the
+  test cleanup assume.
+
+It was written for an OpenClaw integration that is not being pursued (see
+`docs/openclaw.md`). Fix and add CI, or remove it, before anyone depends on it.