fix(watcher): always tree-kill on stop regardless of childProcess.killed flag

The direct bash child may already be dead from terminal SIGINT while
grandchildren (tsrun, devserver) are still running. Removing the .killed
guard ensures tree-kill always runs to clean up the entire process tree.

ts/tswatch.classes.watcher.ts

@@ -202,7 +202,9 @@ export class Watcher {
       clearTimeout(this.debounceTimer);
     }
     await this.smartwatchInstance.stop();
-    if (this.currentExecution && !this.currentExecution.childProcess.killed) {
+    if (this.currentExecution) {
+      // Always tree-kill — even if the direct child is dead (.killed === true),
+      // grandchildren (e.g. tsrun, devserver) may still be running.
       await this.currentExecution.kill();
     }
   }