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- README, QUICKSTART, USE_CASES, ROADMAP (Track 7 withdrawn), CLAUDE.md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- packages/clawhdf5-node: marked unpublished and broken, "private": true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/USE_CASES.md

@@ -42,37 +42,10 @@ conversation → embedding → save to agent.h5
 
 ---
 
-## 2. OpenClaw Memory Upgrade
+## 2. OpenClaw
 
-**Scenario:** You run OpenClaw and the default Markdown + sqlite-vec memory works OK for simple recall but falls short on complex queries like "what did we decide about the deployment architecture last Tuesday?" or "who's responsible for the billing system?"
-
-**Problem:** Markdown files have no semantic structure. sqlite-vec does flat vector search — no keyword fusion, no re-ranking, no temporal reasoning, no knowledge graph.
-
-**ClawhDF5 solution:**
-
-```bash
-# Migrate existing memories
-clawhdf5 --path memory.h5 create --agent-id openclaw --dim 384
-
-# Import your MEMORY.md and daily logs
-# (programmatically via ClawhdfBackend::ingest_markdown)
-```
-
-Then in your OpenClaw config (future):
-```json
-{
-  "memory": {
-    "backend": "clawhdf5",
-    "path": "~/.openclaw/agents/main/memory.h5"
-  }
-}
-```
-
-**What changes:**
-- "What did we discuss last Tuesday?" → temporal index finds the session, returns memories from that time range
-- "Who owns the billing system?" → knowledge graph traversal: billing_system → owned_by → Alice
-- "Preferences about deployment" → hybrid search (vector + BM25) finds relevant memories even with different wording
-- Bad search results get filtered out by confidence rejection instead of confusing the agent
+Not supported: clawhdf5 is not an OpenClaw memory plugin, and the config this
+section used to show was never valid. See [openclaw.md](openclaw.md).
 
 ---