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>

webui.html

@@ -133,10 +133,10 @@ svg.day-timeline{display:block;width:100%;height:22px}
   <button id="refresh-btn" aria-label="Refresh file list">&#8635; Refresh</button>
 </header>
 <div class="controls-bar">
-  <label for="threshold-input">Analysis threshold:</label>
-  <input type="number" id="threshold-input" min="0" max="1" step="0.005" value="0.05"
-    aria-describedby="threshold-hint">
-  <span id="threshold-hint" class="controls-hint">RMS amplitude 0–1 (linear; 0.05 ≈ −26 dBFS) · sections above this are marked loud</span>
+  <label for="margin-input">Loudness margin:</label>
+  <input type="number" id="margin-input" min="1" max="60" step="1" value="12"
+    aria-describedby="margin-hint">
+  <span id="margin-hint" class="controls-hint">dB above background noise — sections that rise this far above the rolling noise floor are marked loud</span>
   <label for="preroll-input" style="margin-left:16px">Pre-roll:</label>
   <input type="number" id="preroll-input" min="0" max="30" step="0.5" value="3"
     aria-describedby="preroll-hint">
@@ -321,15 +321,15 @@ function seekToSection(idx, filename, startSec, endSec, sectionIdx) {
   }
 }
 
-// filename|threshold|gap -> analysis result, so re-renders (filtering,
+// filename|margin|gap -> analysis result, so re-renders (filtering,
 // refresh) never refetch what this session already has
 const analysisCache = new Map();
 
-async function fetchAnalysis(filename, threshold, minGap, force = false) {
-  const key = `${filename}|${threshold}|${minGap}`;
+async function fetchAnalysis(filename, margin, minGap, force = false) {
+  const key = `${filename}|${margin}|${minGap}`;
   if (!force && analysisCache.has(key)) return analysisCache.get(key);
   const r = await fetch('/api/analyze?file='+encodeURIComponent(filename)
-    +'&threshold='+encodeURIComponent(threshold)
+    +'&margin='+encodeURIComponent(margin)
     +'&min_gap='+encodeURIComponent(minGap));
   const d = await r.json();
   if (!d.error) analysisCache.set(key, d);
@@ -340,15 +340,15 @@ async function analyse(idx, filename, cell, btn, force = false) {
   btn.disabled = true;
   btn.textContent = '…';
   cell.innerHTML = '<div class="spin" aria-live="polite" aria-busy="true">Analysing…</div>';
-  const threshold = document.getElementById('threshold-input').value || '0.05';
-  const minGap    = document.getElementById('min-gap-input').value || '2';
+  const margin = document.getElementById('margin-input').value || '12';
+  const minGap = document.getElementById('min-gap-input').value || '2';
   const restoreBtn = () => {
     btn.textContent = 'Analyse'; btn.disabled = false;
     btn.onclick = () => analyse(idx, filename, cell, btn);
     if (!cell.contains(btn)) cell.appendChild(btn);
   };
   try {
-    const d = await fetchAnalysis(filename, threshold, minGap, force);
+    const d = await fetchAnalysis(filename, margin, minGap, force);
     if (d.error) {
       cell.innerHTML = `<div class="spin" role="alert">Error: ${esc(d.error)}</div>`;
       restoreBtn(); return;
@@ -357,7 +357,7 @@ async function analyse(idx, filename, cell, btn, force = false) {
     box.appendChild(drawWave(d.rms_display||[], d.sections||[], d.duration||0, filename));
 
     const meta = document.createElement('div'); meta.className='analysis-meta';
-    meta.textContent = `threshold: ${threshold} · gap: ${minGap}s${d.cached ? ' · cached' : ''}`;
+    meta.textContent = `margin: ${margin} dB · gap: ${minGap}s${d.cached ? ' · cached' : ''}`;
     box.appendChild(meta);
 
     const chips = document.createElement('div');
@@ -370,7 +370,8 @@ async function analyse(idx, filename, cell, btn, force = false) {
         const c = document.createElement('button');
         c.className='chip';
         c.title = 'Jump to this section (or use J/K keys)';
-        c.textContent = `${fmtDur(s.start)} – ${fmtDur(s.end)}`;
+        c.textContent = `${fmtDur(s.start)} – ${fmtDur(s.end)}`
+          + (s.score != null ? ` · +${Math.round(s.score)} dB` : '');
         c.addEventListener('click', () => seekToSection(idx, filename, s.start, s.end, si));
         chips.appendChild(c);
       });
@@ -494,8 +495,8 @@ async function updateStorage() {
 // Auto-loading on a mismatch would silently recompute every file.
 function cachedParamsMatch(ca) {
   return ca != null
-    && Number(ca.threshold) === parseFloat(document.getElementById('threshold-input').value)
-    && Number(ca.min_gap)   === parseFloat(document.getElementById('min-gap-input').value);
+    && Number(ca.margin)  === parseFloat(document.getElementById('margin-input').value)
+    && Number(ca.min_gap) === parseFloat(document.getElementById('min-gap-input').value);
 }
 
 // Run the deferred analyses of a freshly expanded day
@@ -769,8 +770,8 @@ async function dayHighlights(dayId, analyzableFiles) {
   progWrap.appendChild(progBar); progWrap.appendChild(progFile);
   contentEl.innerHTML = ''; contentEl.appendChild(progWrap);
 
-  const threshold = document.getElementById('threshold-input').value || '0.05';
-  const minGap    = document.getElementById('min-gap-input').value || '2';
+  const margin = document.getElementById('margin-input').value || '12';
+  const minGap = document.getElementById('min-gap-input').value || '2';
 
   const results = [];
   let nCached = 0, nLive = 0;
@@ -779,7 +780,7 @@ async function dayHighlights(dayId, analyzableFiles) {
     progFile.textContent  = `${i + 1} / ${n} — ${f.name}`;
     progFill.style.width  = `${(i / n) * 100}%`;
     try {
-      const d = await fetchAnalysis(f.name, threshold, minGap);
+      const d = await fetchAnalysis(f.name, margin, minGap);
       if (!d.error) { results.push({ f, data: d }); d.cached ? nCached++ : nLive++; }
     } catch(e) {}
   }
@@ -868,6 +869,7 @@ async function dayHighlights(dayId, analyzableFiles) {
         filename: f.name,
         start: s.start,
         end: s.end,
+        score: s.score,
         absStart: fileStart + s.start,
       });
     });
@@ -888,31 +890,37 @@ async function dayHighlights(dayId, analyzableFiles) {
 
   if (dayActiveSections.length) {
     const MAX_DAY_CHIPS = 50;
-    if (dayActiveSections.length > MAX_DAY_CHIPS) {
+    // When there are too many sections to show them all, show the ones most
+    // worth reviewing: the top MAX_DAY_CHIPS by score, loudest first.
+    let chipList = dayActiveSections.map((sec, si) => ({sec, si}));
+    const truncated = chipList.length > MAX_DAY_CHIPS;
+    if (truncated) {
+      chipList = chipList
+        .sort((a, b) => (b.sec.score || 0) - (a.sec.score || 0))
+        .slice(0, MAX_DAY_CHIPS);
       const note = document.createElement('p');
       note.className = 'quiet';
       note.style.marginTop = '6px';
-      note.textContent = `${dayActiveSections.length} sections — use J / K to navigate`;
+      note.textContent = `${dayActiveSections.length} sections — chips show the top ${MAX_DAY_CHIPS} by loudness; J / K steps through all in time order`;
       box.appendChild(note);
-    } else {
-      const chips = document.createElement('div');
-      chips.className = 'chips';
-      chips.setAttribute('role', 'group');
-      chips.setAttribute('aria-label', 'Day loud sections — click to jump, J/K to step across files');
-      dayActiveSections.forEach((sec, si) => {
-        const c = document.createElement('button');
-        c.className = 'chip';
-        c.title = sec.filename + ' @ ' + fmtDur(sec.start);
-        const d = new Date(sec.absStart * 1000);
-        const hms = d.getHours().toString().padStart(2,'0') + ':'
-                  + d.getMinutes().toString().padStart(2,'0') + ':'
-                  + d.getSeconds().toString().padStart(2,'0');
-        c.textContent = hms;
-        c.addEventListener('click', () => jumpToDaySection(si));
-        chips.appendChild(c);
-      });
-      box.appendChild(chips);
     }
+    const chips = document.createElement('div');
+    chips.className = 'chips';
+    chips.setAttribute('role', 'group');
+    chips.setAttribute('aria-label', 'Day loud sections — click to jump, J/K to step across files');
+    chipList.forEach(({sec, si}) => {
+      const c = document.createElement('button');
+      c.className = 'chip';
+      c.title = sec.filename + ' @ ' + fmtDur(sec.start);
+      const d = new Date(sec.absStart * 1000);
+      const hms = d.getHours().toString().padStart(2,'0') + ':'
+                + d.getMinutes().toString().padStart(2,'0') + ':'
+                + d.getSeconds().toString().padStart(2,'0');
+      c.textContent = hms + (sec.score != null ? ` · +${Math.round(sec.score)} dB` : '');
+      c.addEventListener('click', () => jumpToDaySection(si));
+      chips.appendChild(c);
+    });
+    box.appendChild(chips);
   }
 
   const summary = document.createElement('div');
@@ -1009,10 +1017,10 @@ document.getElementById('filter-clear').addEventListener('click', () => {
   applyFilters();
 });
 
-// Seed threshold and min_gap from server config, then start
+// Seed margin and min_gap from server config, then start
 fetch('/api/config').then(r => r.json()).then(cfg => {
-  if (cfg.threshold != null)
-    document.getElementById('threshold-input').value = cfg.threshold;
+  if (cfg.margin != null)
+    document.getElementById('margin-input').value = cfg.margin;
   if (cfg.min_gap != null)
     document.getElementById('min-gap-input').value = cfg.min_gap;
 }).catch(() => {}).finally(() => load().then(() => setInterval(pollStatus, 5000)));