Rename clicktrack.js — a content blocker was eating it and killing the app

A file called `clicktrack.js` matches the click-tracking telemetry patterns that
EasyPrivacy and similar lists block by substring. In a browser with a content
blocker the request never completes, and because it is a module import that
takes the entire graph with it: main.js never runs, no handler is ever bound,
and every control in the UI sits there looking correct and doing nothing.

The failure is unusually expensive to diagnose because everything else looks
healthy. The dev server returns 200 with the right MIME type, curl fetches it
fine, node imports it fine, and the app loads perfectly in any browser without a
blocker — which is how it passed every check here. Only the console names it,
and only as one line about a module that failed to load.

Renamed to metronome.js, which is also the better name for what it does. The
button id went with it, since cosmetic filter rules can hit ids too.

The general rule, recorded at the top of the file: anything shipped to a browser
and named like tracking will be treated as tracking. Avoid click, track,
analytics, pixel, beacon and ad in filenames and URL paths, however honest the
code behind them is.

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

flow-state/README.md

@@ -45,7 +45,7 @@ under the playhead; **lock** protects a section from further rerolls. Every
 parameter the generator chose is exposed under the *scene* tab and can be edited
 live.
 
-The **click track** button (look tab) mixes an audible click onto the detected beat
+The **metronome** button (look tab) mixes an audible click onto the detected beat
 grid. If the clicks don't sit on the beat, tempo detection is wrong and everything
 downstream inherits it — check this first when a track looks off.
 
@@ -133,7 +133,7 @@ Scenes that composite over a background rather than being one declare
 
 ```
 src/
-  audio/      decode, STFT analysis, tempo, segmentation, FeatureTrack, click track
+  audio/      decode, STFT analysis, tempo, segmentation, FeatureTrack, metronome
   engine/     Timeline, Renderer, Layer, Compositor, passes, seeded rng, flash safety
   look/       palette (OKLCH), LookGenerator, ArcDriver
   params/     declarative schema, validation, serialisation