feat: Allow cancellation of in-progress Gemini requests and pre-execution checks

- Implements cancellation for Gemini requests while they are actively being processed by the model.
- Extends cancellation support to the  logic within tools. This allows users to cancel operations during the phase where the system is determining if a tool execution requires user confirmation, which can include potentially long-running pre-flight checks or LLM-based corrections.
- Underlying LLM calls for edit corrections (within  and ) and next speaker checks can now also be cancelled.
- Previously, cancellation of the main request was not possible until text started streaming, and pre-execution checks were not cancellable.
- This change leverages the updated SDK's ability to accept an abort token and threads s throughout the request, tool execution, and pre-execution check lifecycle.

Fixes https://github.com/google-gemini/gemini-cli/issues/531

packages/server/src/tools/tools.ts

@@ -57,6 +57,7 @@ export interface Tool<
    */
   shouldConfirmExecute(
     params: TParams,
+    abortSignal: AbortSignal,
   ): Promise<ToolCallConfirmationDetails | false>;
 
   /**
@@ -137,6 +138,8 @@ export abstract class BaseTool<
   shouldConfirmExecute(
     // eslint-disable-next-line @typescript-eslint/no-unused-vars
     params: TParams,
+    // eslint-disable-next-line @typescript-eslint/no-unused-vars
+    abortSignal: AbortSignal,
   ): Promise<ToolCallConfirmationDetails | false> {
     return Promise.resolve(false);
   }