fix(vscode-ide-companion): resolve all ESLint errors

Fixed unused variable errors in SessionMessageHandler.ts:
- Commented out unused conversation and messages variables

Also includes previous commits:
1. feat(vscode-ide-companion): add upgrade button to CLI version warning
2. fix(vscode-ide-companion): resolve ESLint errors in InputForm component

When the Qwen Code CLI version is below the minimum required version,
the warning message now includes an "Upgrade Now" button that opens
a terminal and runs the npm install command to upgrade the CLI.

Added tests to verify the functionality works correctly.

packages/vscode-ide-companion/src/webview/MessageHandler.ts

@@ -73,11 +73,4 @@ export class MessageHandler {
   appendStreamContent(chunk: string): void {
     this.router.appendStreamContent(chunk);
   }
-
-  /**
-   * Check if saving checkpoint
-   */
-  getIsSavingCheckpoint(): boolean {
-    return this.router.getIsSavingCheckpoint();
-  }
 }