Fix false exit-code-1 in terminal and improve error handling

main.js:
- Remove pre-flight sendProcessError check that was firing code 1 before
  any process started (fs.existsSync check could fail on Windows even when
  file exists, e.g. case sensitivity or path format issues)
- Add _userStopped flag so Stop button on Windows (which kills with exit
  code 1) is reported as null (stopped) not an error in the renderer
- Apply _userStopped to both pty and pipe-mode close/exit handlers

Python scripts (downloader, extract_caption, semantic_alignment, note_generation):
- Wrap main() call in broad try/except to catch all unhandled runtime
  exceptions, print a clear [error] message + traceback, and exit 1
  (instead of bare Python traceback with no context)
- KeyboardInterrupt exits cleanly with code 0

Author: nodeeeeee

downloader.py

@@ -1266,4 +1266,15 @@ def main() -> None:
 
 
 if __name__ == "__main__":
-    main()
+    try:
+        main()
+    except KeyboardInterrupt:
+        print("\n[info] Interrupted by user.")
+        sys.exit(0)
+    except SystemExit:
+        raise
+    except Exception as _exc:
+        import traceback
+        print(f"\n[error] Unexpected error: {_exc}")
+        traceback.print_exc()
+        sys.exit(1)

electron/main.js

@@ -337,37 +337,15 @@ function torchIndexUrl(cuda) {
 }
 
 // ── Active process state ──────────────────────────────────────────────────────
-let activeProc  = null;
-let installProc = null;
-let mainWindow  = null;
+let activeProc    = null;
+let installProc   = null;
+let mainWindow    = null;
+let _userStopped  = false;  // set true when user clicks Stop, so close code is ignored
 
 // ── Subprocess runner (pipeline scripts) ─────────────────────────────────────
-function sendProcessError(msg) {
-  mainWindow?.webContents.send('process:data', msg + '\n');
-  mainWindow?.webContents.send('process:done', { code: 1 });
-}
-
 function runProcess(cmd) {
   if (activeProc) return { error: 'Already running — stop it first.' };
-
-  // ── Pre-flight validation ──────────────────────────────────────────────────
-  const [pythonExe, scriptFile] = cmd;
-
-  // Validate Python executable: if it looks like an absolute path, check it exists.
-  if (pythonExe && path.isAbsolute(pythonExe) && !fs.existsSync(pythonExe)) {
-    sendProcessError(
-      `[error] Python executable not found: ${pythonExe}\n` +
-      `[error] Please install the ML environment from Settings → ML Environment,\n` +
-      `[error] or configure a valid Python path in Settings → Connection.`
-    );
-    return { ok: true };
-  }
-
-  // Validate script file exists.
-  if (scriptFile && path.isAbsolute(scriptFile) && !fs.existsSync(scriptFile)) {
-    sendProcessError(`[error] Script not found: ${scriptFile}`);
-    return { ok: true };
-  }
+  _userStopped = false;
 
   const outDir = getOutputDir();
   fs.mkdirSync(outDir, { recursive: true });
@@ -395,7 +373,11 @@ function runProcess(cmd) {
       });
       ptyProc.onExit(({ exitCode }) => {
         activeProc = null;
-        mainWindow?.webContents.send('process:done', { code: exitCode });
+        if (_userStopped) {
+          mainWindow?.webContents.send('process:done', { code: null });
+        } else {
+          mainWindow?.webContents.send('process:done', { code: exitCode });
+        }
       });
       return { ok: true };
     } catch { /* fall through to pipe mode */ }
@@ -413,9 +395,15 @@ function runProcess(cmd) {
   proc.stderr.on('data', d => mainWindow?.webContents.send('process:data', d.toString('utf8')));
   proc.on('close', code => {
     activeProc = null;
-    mainWindow?.webContents.send('process:done', { code });
+    if (_userStopped) {
+      // User clicked Stop — don't treat as an error regardless of exit code
+      mainWindow?.webContents.send('process:done', { code: null });
+    } else {
+      mainWindow?.webContents.send('process:done', { code: code ?? 1 });
+    }
   });
   proc.on('error', err => {
+    if (_userStopped) { activeProc = null; return; }
     activeProc = null;
     const hint = err.code === 'ENOENT'
       ? `\n[error] Could not find executable: ${prog}\n[error] Install the ML environment from Settings → ML Environment.`
@@ -428,11 +416,14 @@ function runProcess(cmd) {
 
 function stopProcess() {
   if (!activeProc) return;
+  _userStopped = true;
   try {
     if (typeof activeProc.kill === 'function') activeProc.kill();
     else activeProc.kill('SIGTERM');
   } catch {}
   activeProc = null;
+  // Send 'stopped' event immediately so the renderer doesn't wait for close
+  mainWindow?.webContents.send('process:done', { code: null });
 }
 
 // ── ML environment installer ──────────────────────────────────────────────────

extract_caption.py

@@ -431,4 +431,15 @@ def main() -> None:
 
 
 if __name__ == "__main__":
-    main()
+    try:
+        main()
+    except KeyboardInterrupt:
+        print("\n[info] Interrupted by user.")
+        sys.exit(0)
+    except SystemExit:
+        raise
+    except Exception as _exc:
+        import traceback
+        print(f"\n[error] Unexpected error: {_exc}")
+        traceback.print_exc()
+        sys.exit(1)

note_generation.py

@@ -1394,4 +1394,15 @@ def main() -> None:
 
 
 if __name__ == "__main__":
-    main()
+    try:
+        main()
+    except KeyboardInterrupt:
+        print("\n[info] Interrupted by user.")
+        sys.exit(0)
+    except SystemExit:
+        raise
+    except Exception as _exc:
+        import traceback
+        print(f"\n[error] Unexpected error: {_exc}")
+        traceback.print_exc()
+        sys.exit(1)

semantic_alignment.py

@@ -1189,4 +1189,15 @@ def main() -> None:
 
 
 if __name__ == "__main__":
-    main()
+    try:
+        main()
+    except KeyboardInterrupt:
+        print("\n[info] Interrupted by user.")
+        sys.exit(0)
+    except SystemExit:
+        raise
+    except Exception as _exc:
+        import traceback
+        print(f"\n[error] Unexpected error: {_exc}")
+        traceback.print_exc()
+        sys.exit(1)