fix(mcp): ensure MCP servers are gracefully shut down on CLI exit

This commit introduces a cleanup mechanism for MCP servers to prevent them from being orphaned or terminated abruptly when the Gemini CLI exits.

- Added a `dispose()` method to the `Config` class in `packages/core` that triggers `McpClientManager.stop()`.
- Registered `config.dispose()` as a cleanup handler in the main CLI entry point (`packages/cli/src/gemini.tsx`).

This ensures that the `stop()` method of `McpClientManager` is invoked, allowing for the proper closing of transport connections (sending SIGTERM/closing streams) to downstream MCP servers.

Author: ergunsh

packages/cli/src/gemini.tsx

@@ -477,6 +477,9 @@ export async function main() {
     // This ensures telemetry (including SessionEnd hooks) is properly flushed on exit
     registerTelemetryConfig(config);
 
+    // Ensure MCP servers are stopped on exit
+    registerCleanup(() => config.dispose());
+
     const policyEngine = config.getPolicyEngine();
     const messageBus = config.getMessageBus();
     createPolicyUpdater(policyEngine, messageBus);

packages/core/src/config/config.ts

@@ -824,6 +824,15 @@ export class Config {
     await this.geminiClient.initialize();
   }
 
+  /**
+   * Disposes of resources held by the config.
+   */
+  async dispose(): Promise<void> {
+    if (this.mcpClientManager) {
+      await this.mcpClientManager.stop();
+    }
+  }
+
   getContentGenerator(): ContentGenerator {
     return this.contentGenerator;
   }