style: increase ReadoutPanel font sizes and add CSV test fixture for data logging

tests/test_csv_recorder.py

@@ -38,3 +38,70 @@ def test_recorded_data_rows_are_readable(tmp_path):
     assert records[0].values == [149.0, 148.0]
     assert records[1].time == 0.5
     assert records[1].values == [149.5, 148.5]
+
+# ===== write_segment (P3.3) =====
+def _make_zwafer_csv(tmp_path, rows=5):
+    sensors = [Sensor("1", 0.0, 1.0), Sensor("2", 1.0, 0.0)]
+    path = tmp_path / "src.csv"
+    rec = CsvRecorder()
+    rec.start(str(path), sensors, serial="A12")
+    for i in range(rows):
+        rec.write(Frame(seq=i, time=i * 0.5, values=[100.0 + i, 200.0 + i]))
+    rec.stop()
+    return path
+
+
+def test_write_segment_zwafer_slice(tmp_path):
+    src = _make_zwafer_csv(tmp_path, rows=5)
+    dest = tmp_path / "seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 1, 3) is True
+
+    records = read_data_records(str(dest))
+    assert len(records) == 3
+    assert records[0].values == [101.0, 201.0]
+    assert records[-1].values == [103.0, 203.0]
+
+    # header survives → still parses as a wafer CSV
+    data, _ = ZWaferParser().parse(str(dest))
+    assert data is not None
+    assert [s.label for s in data.sensors] == ["1", "2"]
+
+
+def test_write_segment_full_range(tmp_path):
+    src = _make_zwafer_csv(tmp_path, rows=4)
+    dest = tmp_path / "seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 0, 3) is True
+    assert len(read_data_records(str(dest))) == 4
+
+
+def test_write_segment_out_of_range(tmp_path):
+    src = _make_zwafer_csv(tmp_path, rows=3)
+    dest = tmp_path / "seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 10, 20) is False
+    assert not dest.exists()
+
+
+def test_write_segment_invalid_range(tmp_path):
+    src = _make_zwafer_csv(tmp_path, rows=3)
+    dest = tmp_path / "seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 2, 1) is False
+    assert CsvRecorder.write_segment(str(dest), str(src), -1, 1) is False
+
+
+def test_write_segment_official_csv(tmp_path):
+    # official format: row 0 = sensor names, rows 1+ = values only
+    src = tmp_path / "A00001-x.csv"
+    src.write_text(
+        "Sensor1,Sensor2\n"
+        "10.0,20.0\n"
+        "11.0,21.0\n"
+        "12.0,22.0\n",
+        encoding="utf-8",
+    )
+    dest = tmp_path / "A00001-x_seg.csv"
+    assert CsvRecorder.write_segment(str(dest), str(src), 1, 2) is True
+    lines = dest.read_text(encoding="utf-8").splitlines()
+    assert lines[0] == "Sensor1,Sensor2"
+    assert lines[1] == "11.0,21.0"
+    assert lines[2] == "12.0,22.0"
+    assert len(lines) == 3