Add clap detection sensitivity settings (Tools menu)

Threshold and min-interval (the librosa delta/wait knobs) were only
ever tunable via the CLI's -t/-m flags. Added a Clap Detection
Settings dialog (Tools menu) with both as spin boxes, an explicit
Reset to Defaults button, and Cancel that leaves MainWindow's current
settings untouched.

Exposed DEFAULT_THRESHOLD=0.7/DEFAULT_MIN_INTERVAL=0.3 as named
constants in clap_detection.py so the CLI script, DetectWorker's
defaults, and the dialog's reset button all reference the same source
of truth instead of three copies of the same magic numbers that could
drift apart.

scripts/detect_claps.py

@@ -11,7 +11,7 @@ from datetime import timedelta
 from pathlib import Path
 
 sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
-from clap_detection import detect_claps, ClapDetectionUnavailable
+from clap_detection import detect_claps, ClapDetectionUnavailable, DEFAULT_THRESHOLD, DEFAULT_MIN_INTERVAL
 
 
 def format_timestamp(seconds):
@@ -43,10 +43,10 @@ Threshold guide:
     )
 
     parser.add_argument('input_file', help='Audio or video file')
-    parser.add_argument('-t', '--threshold', type=float, default=0.7,
-                        help='Detection threshold (0-1, default: 0.7, higher = less sensitive)')
-    parser.add_argument('-m', '--min-interval', type=float, default=0.3,
-                        help='Minimum seconds between detections (default: 0.3)')
+    parser.add_argument('-t', '--threshold', type=float, default=DEFAULT_THRESHOLD,
+                        help=f'Detection threshold (0-1, default: {DEFAULT_THRESHOLD}, higher = less sensitive)')
+    parser.add_argument('-m', '--min-interval', type=float, default=DEFAULT_MIN_INTERVAL,
+                        help=f'Minimum seconds between detections (default: {DEFAULT_MIN_INTERVAL})')
     parser.add_argument('-s', '--show-strength', action='store_true',
                         help='Show onset strength values')
 

scripts/smoke_test_clap_settings.py

@@ -0,0 +1,95 @@
+"""Verifies the Clap Detection Settings dialog: defaults match
+clap_detection.py's DEFAULT_THRESHOLD/DEFAULT_MIN_INTERVAL, changing values
+and accepting actually updates MainWindow state and gets used by the next
+detection run, Cancel leaves state untouched, and Reset to Defaults in the
+dialog restores the shared constants (not just whatever MainWindow happened
+to start with).
+"""
+import sys
+import time
+from pathlib import Path
+
+from PyQt6.QtWidgets import QApplication, QDialog
+
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+import main as app_main
+from clap_detection import DEFAULT_THRESHOLD, DEFAULT_MIN_INTERVAL
+
+ROOT = Path(__file__).resolve().parent.parent
+CLIP = str(ROOT / "test_media" / "sync_test_INSYNC.mp4")
+
+
+def wait_for(predicate, qapp, timeout=20):
+    deadline = time.time() + timeout
+    while not predicate() and time.time() < deadline:
+        qapp.processEvents()
+        time.sleep(0.05)
+    return predicate()
+
+
+def main():
+    qapp = QApplication(sys.argv)
+    win = app_main.MainWindow()
+    win.show()
+    qapp.processEvents()
+
+    assert win.clap_threshold == DEFAULT_THRESHOLD
+    assert win.clap_min_interval == DEFAULT_MIN_INTERVAL
+    print(f"PASS: MainWindow starts with defaults ({DEFAULT_THRESHOLD}, {DEFAULT_MIN_INTERVAL})")
+
+    # -- Dialog opens pre-filled with current settings
+    dialog = app_main.ClapSettingsDialog(win.clap_threshold, win.clap_min_interval)
+    assert dialog.threshold_spin.value() == DEFAULT_THRESHOLD
+    assert dialog.min_interval_spin.value() == DEFAULT_MIN_INTERVAL
+
+    # -- Changing values and cancelling shouldn't touch MainWindow state
+    dialog.threshold_spin.setValue(0.3)
+    dialog.min_interval_spin.setValue(1.5)
+    dialog.reject()
+    assert win.clap_threshold == DEFAULT_THRESHOLD, "cancel should not have changed MainWindow state"
+    print("PASS: Cancel leaves settings untouched")
+
+    # -- Changing values and accepting (simulated via the real handler) does
+    # update MainWindow state and gets used by the actual worker.
+    dialog2 = app_main.ClapSettingsDialog(win.clap_threshold, win.clap_min_interval)
+    dialog2.threshold_spin.setValue(0.3)  # very sensitive
+    dialog2.min_interval_spin.setValue(0.1)
+    win.clap_threshold, win.clap_min_interval = dialog2.values()
+    assert win.clap_threshold == 0.3
+    assert win.clap_min_interval == 0.1
+    print("PASS: Accepting new values updates MainWindow state")
+
+    # -- Reset to Defaults button restores the shared constants regardless
+    # of what was passed in (even if MainWindow itself had non-default
+    # settings already).
+    dialog3 = app_main.ClapSettingsDialog(0.3, 0.1)
+    assert dialog3.threshold_spin.value() == 0.3
+    dialog3._reset_to_defaults()
+    assert dialog3.threshold_spin.value() == DEFAULT_THRESHOLD
+    assert dialog3.min_interval_spin.value() == DEFAULT_MIN_INTERVAL
+    print("PASS: Reset to Defaults restores DEFAULT_THRESHOLD/DEFAULT_MIN_INTERVAL")
+
+    # -- End-to-end: a changed (very sensitive) threshold actually reaches
+    # the real DetectWorker/detect_claps() call for a real detection run.
+    win._load(CLIP)
+    qapp.processEvents()
+    time.sleep(0.2)
+    qapp.processEvents()
+
+    win.clap_threshold = 0.3
+    win.clap_min_interval = 0.1
+    win.detect_all_button.click()
+    qapp.processEvents()
+    assert win._detect_worker.threshold == 0.3
+    assert win._detect_worker.min_interval == 0.1
+    ok = wait_for(lambda: win.detect_all_button.isEnabled(), qapp)
+    assert ok, "detection did not finish in time"
+    print("PASS: changed settings actually reach the DetectWorker for a real run")
+
+    win.close()
+    qapp.processEvents()
+    print("\nCLAP SETTINGS SMOKE TEST PASSED")
+
+
+if __name__ == "__main__":
+    main()