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.

tests/routes/chatSession.test.ts

@@ -96,6 +96,7 @@ describe("generateSessionTitle", () => {
         },
       ],
       abortSession: async () => undefined,
+      removeSession: async () => undefined,
     } as unknown as OpencodeRuntimeAdapter;
 
     const title = await generateSessionTitle(runtime, {