feat: adaptive noise-floor loudness detection with section scoring

Replace the fixed RMS threshold with prominence over a rolling noise
floor (20th percentile per 30s block, min-smoothed so events cannot
raise their own floor, clamped to -54 dBFS). Slow ambience changes such
as rain or daytime traffic hum move the floor instead of flagging
everything; sections now need `margin` dB (default 12) of prominence.

Each section carries a score (peak dB above floor); day-highlight chips
show the top 50 by score when there are too many to list, so the most
striking events are reviewed first.

--threshold is replaced by --margin; analysis caches are now keyed by
margin+min_gap, old threshold-keyed caches never match and are
overwritten on the next analyse. Detector covered by tests/test_web.py.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

tests/test_web.py

@@ -0,0 +1,69 @@
+"""Tests for the adaptive loud-section detector in web.py."""
+
+import math
+
+from web import _loud_sections, _noise_floor_db
+
+WINDOW_DUR = 0.1  # 100 ms windows, as produced by WINDOW_SAMPLES at 48 kHz
+
+
+def _run(rms, margin_db=12.0, min_gap=2.0):
+    duration = len(rms) * WINDOW_DUR
+    return _loud_sections(rms, WINDOW_DUR, duration, margin_db, min_gap)
+
+
+def test_burst_above_quiet_floor_is_detected():
+    rms = [0.002] * 1200          # 2 min of quiet ambience (−54 dBFS)
+    rms[600:610] = [0.05] * 10    # 1 s burst at −26 dBFS (+28 dB)
+    sections = _run(rms)
+    assert len(sections) == 1
+    s = sections[0]
+    assert s['start'] == 60.0
+    assert 60.5 <= s['end'] <= 62.0
+    assert 26.0 <= s['score'] <= 30.0
+
+
+def test_slow_ambience_swell_is_not_detected():
+    # Level rises 20 dB over 10 minutes and back down — e.g. rain setting in.
+    # The old fixed threshold would have flagged the entire loud half.
+    up   = [0.002 * 10 ** (i / 6000 * 1.0) for i in range(6000)]   # −54 → −34 dB
+    down = list(reversed(up))
+    assert _run(up + down) == []
+
+
+def test_burst_still_detected_on_loud_ambience():
+    # Same +28 dB prominence as the quiet test, but on a 20 dB louder floor.
+    rms = [0.02] * 1200
+    rms[600:610] = [0.5] * 10
+    sections = _run(rms)
+    assert len(sections) == 1
+    assert sections[0]['start'] == 60.0
+
+
+def test_min_rms_floor_suppresses_blips_in_digital_silence():
+    rms = [0.000001] * 1200
+    rms[600:605] = [0.004] * 5    # −48 dBFS: audible blip, but below MIN_RMS+12dB
+    assert _run(rms) == []
+    rms[600:605] = [0.05] * 5     # −26 dBFS clearly clears the clamped floor
+    assert len(_run(rms)) == 1
+
+
+def test_min_gap_merges_nearby_bursts():
+    rms = [0.002] * 1200
+    rms[600:605] = [0.05] * 5
+    rms[615:620] = [0.05] * 5     # 1 s gap < 2 s min_gap → one section
+    rms[900:905] = [0.05] * 5     # 28 s away → separate section
+    sections = _run(rms)
+    assert len(sections) == 2
+    assert sections[0]['start'] == 60.0
+    assert sections[0]['end'] >= 61.5
+    assert sections[1]['start'] == 90.0
+
+
+def test_noise_floor_tracks_blocks_and_ignores_short_events():
+    quiet_db = 20 * math.log10(0.002)
+    db = [quiet_db] * 1200
+    db[600:650] = [-20.0] * 50    # 5 s event must not raise its own floor
+    floor = _noise_floor_db(db, WINDOW_DUR)
+    assert len(floor) == len(db)
+    assert all(abs(f - quiet_db) < 1.0 for f in floor)