feat(FN-2701): route OpenClaw runtime sessions through gateway client

- Add a dedicated gateway client seam and wire runtime adapter sessions through the new request path
- Remove legacy engine-guard/pi seam exports and align runtime types with gateway-facing behavior
- Fix gateway request/stream handling by preventing duplicate user turns, stabilizing tool-call callbacks, and adding a no-op session dispose hook
- Expand plugin test coverage for gateway client, adapter, and index behavior and document runtime gateway behavior in the README

plugins/fusion-plugin-openclaw-runtime/package.json

@@ -21,7 +21,6 @@
     "test": "vitest run --silent=passed-only --reporter=dot"
   },
   "dependencies": {
-    "@fusion/engine": "workspace:*",
     "@fusion/plugin-sdk": "workspace:*"
   },
   "devDependencies": {