fix(core): track PIDs independently to survive removeProcess() race during shutdown

The direct child process may die from terminal SIGINT before ProcessLifecycle
runs shutdown, causing removeProcess() to clear it. Now killAll() uses a
persistent trackedPids Set that is never cleared by removeProcess(), ensuring
grandchild process trees are always killed.

ts/smartexit.classes.lifecycle.ts

@@ -187,22 +187,18 @@ export class ProcessLifecycle {
     });
   }
 
-  /** Synchronous last-resort: SIGKILL any remaining child processes. */
+  /** Synchronous last-resort: SIGKILL any remaining tracked PIDs. */
   private handleExit(): void {
     const instances = ProcessLifecycle.getInstances();
     let killed = 0;
 
     for (const instance of instances) {
-      const processes = instance.processesToEnd.getArray();
-      for (const child of processes) {
-        const pid = child.pid;
-        if (pid && !child.killed) {
-          try {
-            process.kill(pid, 'SIGKILL');
-            killed++;
-          } catch {
-            // Process may already be dead
-          }
+      for (const pid of instance.trackedPids) {
+        try {
+          process.kill(pid, 'SIGKILL');
+          killed++;
+        } catch {
+          // Process already dead
         }
       }
     }