feat(agent): unify MCP tools and adopt Responses delivery

Move project and host queries into native MCP with host-owned OAuth/context,
while retaining memory, skills, actions and publication plugins. Add nearby-model
queries and explicit chat/task/learning model defaults.

Adopt Responses HTTP/SSE and native steer/queue inbox delivery, preserving scoped
session ownership, pending input edits and investigation communication.

Disable local-provider discovery: Server /health allowed native vLLM to probe
/v1/models on port 8000. A native before/after regression prevents recurrence.

Validation: 170 focused Bun tests; service/plugin typechecks; native discovery,
provider-discovery and input-inbox smoke checks; no paid model inference.

package.json

@@ -14,12 +14,15 @@
     "check:openapi": "bun run generate:openapi && git diff --exit-code -- openapi/openapi.json src/generated/server-api.d.ts",
     "check": "bun run typecheck && bun run typecheck:opencode",
     "check:models": "bun scripts/check-models.ts",
+    "check:websearch": "bun scripts/check-websearch.ts",
     "start": "bun src/server.ts",
     "start:integration:isolated": "bun scripts/start-isolated-integration.ts",
     "start:prod": "bun run check && bun src/server.ts"
   },
   "dependencies": {
-    "@opencode/client": "2.0.24",
+    "@modelcontextprotocol/client": "2.3.1",
+    "@modelcontextprotocol/server": "2.3.1",
+    "@opencode/client": "2.0.27",
     "ai": "7.0.8",
     "ajv": "^8.20.0",
     "cors": "^2.8.5",