chore: apply linting fixes and expand ruff coverage to test suite

tests/test_stream_reader.py

@@ -1,7 +1,9 @@
-import time 
+import time
+
 from pygui.backend.models.frame import Frame
 from pygui.serialcomm.stream_reader import StreamReader
 
+
 class FakeTransport:
     """Yield canned data then blocks (returns b'')."""
     def __init__(self, lines):
@@ -28,7 +30,7 @@ class FakeTransport:
         self._pos = idx + 1
         return res
     def close(self): self.closed = True
-    
+
 def parse_line(raw: str, seq: int) -> Frame:
     parts = [float(x) for x in raw.split(",")]
     return Frame(seq = seq, time = parts[0], values = parts[1:])
@@ -38,10 +40,10 @@ def test_reads_frames_and_counts_errors():
     transport = FakeTransport([b"0.0,149,148\n", b"garbage\n", b"0.5,150,149\n"])
     r = StreamReader(transport, parse_line,
                     on_frame = got.append, on_error = lambda e: errors.append(e))
-    
+
     r.start()
     time.sleep(0.1)
     r.stop()
     assert [f.values for f in got] == [[149.0, 148.0], [150.0, 149.0]]
     assert r.error_count == 1
-    assert transport.closed
+    assert transport.closed