Fix weather satellite mode returning false success on SatDump startup failure

Add synchronous startup verification after Popen() — sleep 0.5s and poll
the process before returning to the caller. If SatDump exits immediately
(missing device, bad args), raise RuntimeError with the actual error
message instead of returning status: 'started'. Keep a shorter (2s) async
backup check for slower failures.

Also fix --source_id handling: omit the flag entirely when no serial number
is found instead of passing "0" which SatDump may reject. Change start()
and start_from_file() to return (bool, str|None) tuples so error messages
propagate through to the HTTP response.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

routes/weather_sat.py

@@ -26,48 +26,48 @@ logger = get_logger('intercept.weather_sat')
 weather_sat_bp = Blueprint('weather_sat', __name__, url_prefix='/weather-sat')
 
 # Queue for SSE progress streaming
-_weather_sat_queue: queue.Queue = queue.Queue(maxsize=100)
+_weather_sat_queue: queue.Queue = queue.Queue(maxsize=100)
 
 
-def _progress_callback(progress: CaptureProgress) -> None:
-    """Callback to queue progress updates for SSE stream."""
-    try:
-        _weather_sat_queue.put_nowait(progress.to_dict())
+def _progress_callback(progress: CaptureProgress) -> None:
+    """Callback to queue progress updates for SSE stream."""
+    try:
+        _weather_sat_queue.put_nowait(progress.to_dict())
     except queue.Full:
         try:
             _weather_sat_queue.get_nowait()
             _weather_sat_queue.put_nowait(progress.to_dict())
-        except queue.Empty:
-            pass
-
-
-def _release_weather_sat_device(device_index: int) -> None:
-    """Release an SDR device only if weather-sat currently owns it."""
-    if device_index < 0:
-        return
-
-    try:
-        import app as app_module
-    except ImportError:
-        return
-
-    owner = None
-    get_status = getattr(app_module, 'get_sdr_device_status', None)
-    if callable(get_status):
-        try:
-            owner = get_status().get(device_index)
-        except Exception:
-            owner = None
-
-    if owner and owner != 'weather_sat':
-        logger.debug(
-            'Skipping SDR release for device %s owned by %s',
-            device_index,
-            owner,
-        )
-        return
-
-    app_module.release_sdr_device(device_index)
+        except queue.Empty:
+            pass
+
+
+def _release_weather_sat_device(device_index: int) -> None:
+    """Release an SDR device only if weather-sat currently owns it."""
+    if device_index < 0:
+        return
+
+    try:
+        import app as app_module
+    except ImportError:
+        return
+
+    owner = None
+    get_status = getattr(app_module, 'get_sdr_device_status', None)
+    if callable(get_status):
+        try:
+            owner = get_status().get(device_index)
+        except Exception:
+            owner = None
+
+    if owner and owner != 'weather_sat':
+        logger.debug(
+            'Skipping SDR release for device %s owned by %s',
+            device_index,
+            owner,
+        )
+        return
+
+    app_module.release_sdr_device(device_index)
 
 
 @weather_sat_bp.route('/status')
@@ -178,15 +178,15 @@ def start_capture():
         except queue.Empty:
             break
 
-    # Set callback and on-complete handler for SDR release
-    decoder.set_callback(_progress_callback)
-
-    def _release_device():
-        _release_weather_sat_device(device_index)
+    # Set callback and on-complete handler for SDR release
+    decoder.set_callback(_progress_callback)
+
+    def _release_device():
+        _release_weather_sat_device(device_index)
 
     decoder.set_on_complete(_release_device)
 
-    success = decoder.start(
+    success, error_msg = decoder.start(
         satellite=satellite,
         device_index=device_index,
         gain=gain,
@@ -208,7 +208,7 @@ def start_capture():
         _release_device()
         return jsonify({
             'status': 'error',
-            'message': 'Failed to start capture'
+            'message': error_msg or 'Failed to start capture'
         }), 500
 
 
@@ -310,7 +310,7 @@ def test_decode():
     decoder.set_callback(_progress_callback)
     decoder.set_on_complete(None)
 
-    success = decoder.start_from_file(
+    success, error_msg = decoder.start_from_file(
         satellite=satellite,
         input_file=input_file,
         sample_rate=sample_rate,
@@ -329,7 +329,7 @@ def test_decode():
     else:
         return jsonify({
             'status': 'error',
-            'message': 'Failed to start file decode'
+            'message': error_msg or 'Failed to start file decode'
         }), 500
 
 
@@ -343,9 +343,9 @@ def stop_capture():
     decoder = get_weather_sat_decoder()
     device_index = decoder.device_index
 
-    decoder.stop()
-
-    _release_weather_sat_device(device_index)
+    decoder.stop()
+
+    _release_weather_sat_device(device_index)
 
     return jsonify({'status': 'stopped'})