Rework windows start and stop methods so that command windows dont appear. Stop with signal since we cannot signint.

ui/src/app/api/jobs/[jobID]/stop/route.ts

@@ -6,6 +6,43 @@ import { promisify } from 'util';
 const execAsync = promisify(exec);
 const isWindows = process.platform === 'win32';
 
+// How long a stopping job gets to run its graceful shutdown (KeyboardInterrupt
+// -> on_error -> final DB write) before we assume it is hung and force-kill it.
+const GRACEFUL_STOP_TIMEOUT_MS = 60_000;
+const BACKSTOP_POLL_MS = 2_000;
+
+const isProcessAlive = (pid: number): boolean => {
+  try {
+    process.kill(pid, 0);
+    return true;
+  } catch (e: any) {
+    // EPERM means it exists but belongs to someone else, which still counts.
+    return e?.code === 'EPERM';
+  }
+};
+
+// Windows: the trainer's stop watcher sees the `stop` flag and raises SIGINT
+// inside the process, so the graceful path runs without us sending anything.
+// This backstop only exists for a job that is too hung to notice the flag.
+// Poll (rather than one long timer) so we stop watching the moment the pid
+// dies and never touch a recycled pid.
+const scheduleForceKillBackstop = (pid: number, jobID: string) => {
+  const startedAt = Date.now();
+  const timer = setInterval(() => {
+    if (!isProcessAlive(pid)) {
+      clearInterval(timer);
+      return;
+    }
+    if (Date.now() - startedAt < GRACEFUL_STOP_TIMEOUT_MS) return;
+    clearInterval(timer);
+    console.warn(`Job ${jobID} (pid ${pid}) still alive ${GRACEFUL_STOP_TIMEOUT_MS / 1000}s after stop request, force killing`);
+    execAsync(`taskkill /PID ${pid} /T /F`, { windowsHide: true }).catch(() => {
+      // already gone
+    });
+  }, BACKSTOP_POLL_MS);
+  timer.unref?.();
+};
+
 export async function GET(request: NextRequest, { params }: { params: { jobID: string } }) {
   const { jobID } = await params;
 
@@ -30,9 +67,12 @@ export async function GET(request: NextRequest, { params }: { params: { jobID: s
     console.log(`Attempting to stop job ${jobID} with PID ${job.pid}`);
     try {
       if (isWindows) {
-        // Windows doesn't support SIGINT for arbitrary processes.
-        // Use taskkill with /T (tree) to send a CTRL+C-like termination.
-        await execAsync(`taskkill /PID ${job.pid} /T /F`, { windowsHide: true });
+        // No external SIGINT possible on Windows (the job runs under pythonw
+        // with no console), and none is needed: the `stop` flag written above
+        // is the signal. The trainer's stop watcher polls it and raises
+        // SIGINT in-process, which runs the same KeyboardInterrupt shutdown
+        // as Linux -- final DB write and the closing log lines.
+        scheduleForceKillBackstop(job.pid, jobID);
       } else {
         process.kill(job.pid, 'SIGINT');
       }