refactor(ui): load the capabilities as ES modules (R3a)

The 12 capability <script> tags become type="module". No JS changes — the
capability scripts already self-register on the window.feedBack bus,
version-negotiate (`capabilities.version !== 1` → bail), and self-guard for
idempotency. They never import or call app.js; it is pure pub/sub.

Verified they export nothing by name: no top-level declaration in
capabilities.js or capabilities/*.js is read by any other script, so losing
global scope costs nothing.

This is the first REAL exercise of the ordering fix from #872. A module defers to
after HTML parse, so the capabilities now execute AFTER the document is parsed —
while app.js still calls `window.feedBack.on(...)` at its top level. That only
works because #872 put every classic script into the same deferred queue, where
document order IS execution order: capabilities.js (line 122) still runs before
app.js (line 1237). Had app.js stayed a plain classic script it would have run
during parse, hit a bare `{}`, and died on `.on is not a function`.

A/B against origin/main, 11 probes — capabilities.version, registered
participants (37), compatibility shims (14), the bus, workingTuning, theme,
setViz/showScreen/playSong, mounted plugin screens: IDENTICAL, zero console/page
errors on both. 12 module tags served and executed; pytest 2396, node 1032/1032,
ESLint 0, Codex 0.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

static/v3/index.html

@@ -1244,7 +1244,7 @@
     <script defer src="/static/highway.js"></script>
     <script defer src="/static/vendor/lottie.min.js"></script>
     <script defer src="/static/lottie-api.js"></script>
-    <script type="module" src="/static/app.js"></script>
+    <script defer src="/static/app.js"></script>
     <script defer src="/static/audio-mixer.js"></script>
     <script defer src="/static/vendor/shepherd.min.js"></script>
     <script defer src="/static/tour-engine.js"></script>