test(v1): lock reconnect and disconnect-no-alarm behavior; close T-203

Adds a mid-stream drop recovery test and a pipeline test proving a
disconnected frame yields no events and interrupts a pending suspect
(stream loss never alarms). Live preview and fall detection on the real
Hikvision stream were confirmed on Windows. 74 tests pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

v1/tests/test_video_source.py

@@ -93,6 +93,48 @@ def test_reconnect_waits_then_reopens_with_bounded_backoff():
     assert recovered.image is not None
 
 
+class _FlakyCapture:
+    def __init__(self, read_results):
+        self._read_results = list(read_results)
+
+    def isOpened(self):
+        return True
+
+    def read(self):
+        ok = self._read_results.pop(0) if self._read_results else False
+        return (True, np.zeros((8, 8, 3), dtype=np.uint8)) if ok else (False, None)
+
+    def get(self, _property_id):
+        return 0.0
+
+    def release(self):
+        pass
+
+
+def test_stream_recovers_after_mid_stream_drop():
+    captures = [_FlakyCapture([True]), _OpenCapture()]
+
+    source = VideoSource(
+        "rtsp://demo",
+        mode=SourceMode.STREAM,
+        retry_initial_seconds=2.0,
+        retry_max_seconds=2.0,
+        capture_factory=lambda _source: captures.pop(0),
+    )
+
+    connected = source.read(now=0.0)
+    dropped = source.read(now=1.0)
+    waiting = source.read(now=1.5)
+    recovered = source.read(now=3.0)
+
+    assert connected.status is SourceStatus.CONNECTED
+    assert dropped.status is SourceStatus.RETRYING
+    assert dropped.image is None
+    assert waiting.status is SourceStatus.RETRYING
+    assert recovered.status is SourceStatus.CONNECTED
+    assert recovered.image is not None
+
+
 class _NegativeFirstTimestampCapture:
     def __init__(self):
         self._read_count = 0