Document web UI interactions and content-versioned assets

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015UXA39Sh9coAx4FhRkd8R2

CLAUDE.md

@@ -115,6 +115,12 @@ A custom mastering toolkit that provides metrics to evaluate audio masterings th
 - A static site: decoding and every metric run in the visitor's tab; nothing is
   uploaded or stored. Served with `Content-Security-Policy: connect-src 'none'`
   (`deploy/nginx.conf`), so the page and its worker cannot make network requests
+- The image versions assets by content: everything but `index.html` is copied to
+  `v/<hash>/` and the page's references rewritten (Dockerfile `assets` stage);
+  nginx serves `v/` immutable and the page `no-cache`. Needed because Cloudflare
+  forces browser caching of .js/.css to 4 h, which paired a fresh index.html with
+  a stale app.js (`Cannot set properties of null`). Source `web/index.html` keeps
+  plain relative paths, so serving `web/` directly still works
 - `decode.js` — `AudioFile.__init__` counterpart. WAV/AIFF PCM & float are parsed
   directly with libsndfile scaling (bit-identical to `librosa.load`; Chromium's
   own WAV decoder scales positive int16 by 1/32767). Other formats go through
@@ -133,8 +139,16 @@ A custom mastering toolkit that provides metrics to evaluate audio masterings th
   metric per request, transfers typed arrays back
 - `app.js` — `MainWindow` + `AnalysisResultsManager` + renderer: track list,
   overlay set, per-metric result cache, job queue (foreground jobs jump ahead of
-  background prefetch), uPlot for curves/bands + canvas spectrogram (log axis
-  drawn from linear rows), draggable reference lines per metric, metric hlines
+  background prefetch; LUFS + true peak prefetched first for the metadata
+  panel's loudness summary), uPlot for curves/bands + canvas spectrogram (log
+  axis drawn from linear rows, cached offscreen image). Guide and reference
+  lines are painted in a uPlot draw hook, so dragging a line is a cheap redraw
+  and moves live. One zoom/pan controller serves both renderers: wheel zoom
+  (Ctrl = x only, Shift = y only, over an axis = that axis), rAF-throttled drag
+  pan, double-click reset; `state.zoom` survives redraws and resets when units
+  change. In-plot legend overlay like pyqtgraph's
+- Font: CSS `--font` stack prefers M PLUS 1 Code, else the system UI font;
+  canvas/uPlot text reads the same variable
 - `vendor/` — uPlot 1.6.32, vendored (the CSP only allows same-origin scripts)
 - Needs an HTTP server (module scripts and workers don't load from `file://`),
   but no secure context — plain `http://` on a LAN works