refactor: extract frustration tracking into separate add-on script

Move rage click and dead click detection (35% of script.js) into
script.frustration.js as an optional add-on. Core script drops from
8.1KB to 5.7KB gzipped. Add-on auto-discovers core via window.pulse
polling and supports opt-out via data-no-rage/data-no-dead attributes.

- Expose cleanPath on window.pulse for add-on consumption
- Add script.frustration.js to middleware PUBLIC_ROUTES
- Update integration guides, ScriptSetupBlock, and FrustrationTable
  empty state to reference the add-on script

components/sites/ScriptSetupBlock.tsx

@@ -92,6 +92,9 @@ export default function ScriptSetupBlock({
         <p className="mt-2 text-xs text-neutral-500 dark:text-neutral-400">
           Default: cross-tab (localStorage). Optional: <code className="rounded px-1 bg-neutral-200 dark:bg-neutral-700">data-storage=&quot;session&quot;</code> to opt out (per-tab, ephemeral). Optional: <code className="rounded px-1 bg-neutral-200 dark:bg-neutral-700">data-storage-ttl=&quot;48&quot;</code> to set expiry in hours (default: 24).
         </p>
+        <p className="mt-1.5 text-xs text-neutral-500 dark:text-neutral-400">
+          Optional: add <code className="rounded px-1 bg-neutral-200 dark:bg-neutral-700">{`<script defer src="${APP_URL}/script.frustration.js"></script>`}</code> for rage click and dead click detection.
+        </p>
         <button
           type="button"
           onClick={copyScript}