feat(mcp): restrict grep_app tools to librarian agent only (#395)

* feat(mcp): restrict grep_app tools to librarian agent only

Reduces token usage by disabling grep_app MCP tools globally and enabling them only for the librarian agent, which uses them for GitHub code search during documentation lookups.

Changes:
- Add grep_app_* tool disable globally in config.tools
- Add grep_app_* tool enable for librarian agent
- Remove grep_app references from explore agent prompt (no access)

Closes #394

* chore: changes by sisyphus-dev-ai

---------

Co-authored-by: sisyphus-dev-ai <sisyphus-dev-ai@users.noreply.github.com>

src/index.ts

@@ -489,6 +489,7 @@ const OhMyOpenCodePlugin: Plugin = async (ctx) => {
 
       config.tools = {
         ...config.tools,
+        "grep_app_*": false, // Disable grep_app tools globally to reduce token usage (only librarian needs them)
       };
 
       if (config.agent.explore) {
@@ -501,6 +502,7 @@ const OhMyOpenCodePlugin: Plugin = async (ctx) => {
         config.agent.librarian.tools = {
           ...config.agent.librarian.tools,
           call_omo_agent: false,
+          "grep_app_*": true,
         };
       }
       if (config.agent["multimodal-looker"]) {