fix(runtime): restore v0.9.0 reranker/graph path and hook compatibility

[bharatindia123-a11y]

Summary

• restore the v0.9.0 core runtime path where reranking and graph access were regressing in live OpenClaw usage
• fix Falkor graph read/write handling behind the Missing parameters failures
• keep the OpenClaw hook aligned with the current v0.9.0 server/runtime behavior

Scope

This PR is the core-runtime / integration patch.
It complements, rather than replaces, PR #19:

• PR fix(mcp): send search via POST and preflight oversized store payloads #19 fixes the MCP client path (tools/mcp/server.py)
• this PR fixes the runtime + graph + OpenClaw hook path (tools/brain/* + hooks/openclaw-mem/handler.js)

Files changed

• tools/brain/cross_encoder.py
• tools/brain/graph.py
• tools/brain/search.py
• tools/brain/server.py
• hooks/openclaw-mem/handler.js

Verification

• python -m py_compile tools/brain/cross_encoder.py tools/brain/graph.py tools/brain/search.py tools/brain/server.py
• node --check hooks/openclaw-mem/handler.js
• curl http://127.0.0.1:7777/health
• curl -X POST http://127.0.0.1:7777/search ...

Notes

• This checkout did not currently have the repo's dev extras installed locally, so pytest, ruff, and mypy were not available from the repo venv during PR prep.
• Live smoke verification against the running Rasputin service succeeded after rebasing this patch onto the current v0.9.0 tag commit.
• If desired later, the OpenClaw hook change can be split out, but I think keeping the live regression path together makes review easier for this release-fix pass.

🤖 This PR was created by an AI coding agent
🤖 This was written by an AI coding agent

[bharatindia123-a11y]

Clarifying scope: PR #19 is the MCP-layer fix (POST /search + store-size preflight), while this PR fixes the core runtime / graph / OpenClaw hook regression path that showed up in the live v0.9.0 deployment. I kept them separate so the MCP transport fix can be reviewed independently from the runtime + integration fix.\n\n🤖 This was written by an AI coding agent

[bharatindia123-a11y]

Adding the exact live symptoms observed in production-style usage (OpenClaw hitting the local Rasputin service on 127.0.0.1:7777 after the v0.9.0 upgrade):

• /health and /search were both still responding, so this was not a total outage
• but /health was still reporting "version": "0.8.0", which made the running service look older than the deployed code
• the reranker was still reporting down/degraded in the live service path
• FalkorDB graph operations were logging Missing parameters
• in practice that meant graph commit/read behavior was noisy/broken while Qdrant-backed search could still appear superficially healthy
• the live logs also showed the failure pattern as Missing parameters / cross-encoder-related errors rather than a clean hard crash

After this patch set, the live verification path improved to: reranker up, /search 200, and no Missing parameters / cross-encoder errors in the live log.

🤖 This was written by an AI coding agent