feat: waveform drag-select + wheel zoom (selection_changed/view_changed)

tests/test_ui_structure.py

@@ -414,6 +414,32 @@ def test_waveform_view_and_selection(win):
     assert w.selection() is None
 
 
+def test_waveform_drag_emits_selection(win):
+    w = win._wave
+    w.resize(400, 96)
+    w.set_view(10.0, 4.0)
+    w.set_selection(11.0, 13.0)
+    got = []
+    w.selection_changed.connect(lambda s, e: got.append((s, e)))
+    # new selection: press near t=10.5 (not on a handle), drag to t=13.5, release
+    w._begin_drag_at_x(w._t_to_px(10.5))
+    w._drag_to_x(w._t_to_px(13.5))
+    w._end_drag()
+    assert got, "selection_changed should fire on release"
+    s, e = w.selection()
+    assert 10.0 <= s < e <= 14.0
+
+
+def test_waveform_zoom_emits_view(win):
+    w = win._wave
+    w.resize(400, 96)
+    w.set_view(10.0, 4.0)
+    seen = []
+    w.view_changed.connect(lambda s, d: seen.append((s, d)))
+    w._zoom_at_x(200, 0.5)          # zoom in about the middle
+    assert seen and seen[-1][1] < 4.0
+
+
 def test_audition_button_present_and_safe(win):
     from PyQt6.QtWidgets import QPushButton
     assert isinstance(win._btn_audio_play, QPushButton)