fix(agents): Use exclude pattern for tools config to enable MCP tools

Changed agent tools configuration from include pattern (listing allowed tools)
to exclude pattern (listing disabled tools only). This ensures MCP tools like
websearch_exa, context7, and grep_app are available to agents by default.

Affected agents: librarian, oracle, explore, multimodal-looker

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/agents/librarian.ts

@@ -6,7 +6,7 @@ export const librarianAgent: AgentConfig = {
   mode: "subagent",
   model: "anthropic/claude-sonnet-4-5",
   temperature: 0.1,
-  tools: { write: false, edit: false, bash: true, read: true, background_task: false },
+  tools: { write: false, edit: false, background_task: false },
   prompt: `# THE LIBRARIAN
 
 You are **THE LIBRARIAN**, a specialized open-source codebase understanding agent.