feat(core): implement session isolation for agent and claude executions

- Add run_id/session_id based event isolation for concurrent executions
- Enhance process registry with graceful shutdown and fallback kill methods
- Implement session-specific event listeners in React components
- Add proper process cleanup with timeout handling
- Support both isolated and backward-compatible event emissions
- Improve error handling and logging for process management

This change prevents event crosstalk between multiple concurrent agent/claude sessions
running simultaneously, ensuring proper isolation and user experience.

src/lib/api.ts

@@ -1027,9 +1027,10 @@ export const api = {
 
   /**
    * Cancels the currently running Claude Code execution
+   * @param sessionId - Optional session ID to cancel a specific session
    */
-  async cancelClaudeExecution(): Promise<void> {
-    return invoke("cancel_claude_execution");
+  async cancelClaudeExecution(sessionId?: string): Promise<void> {
+    return invoke("cancel_claude_execution", { sessionId });
   },
 
   /**