Initial commit: Learning Lab Express

Includes fixes found while reviewing the app:
- Results: open each result by a type+agent+id key, so a video and a
  material draft with the same id no longer open each other's popup
- AuthGate: clear the query cache during render, before pages build their
  queries, and remount pages on organization switch (pages no longer stay
  on skeletons for up to a minute after sign-in or refresh)
- Instruction: keep only failed rules after a partial approve, so retrying
  does not create the successful schedules twice; drop the monthly note
  once count or frequency is edited
- Parser/schedules: never schedule a count below one
- Audio: ignore the end event of a cancelled utterance when changing speed
- Downloads: revoke the object URL later so Safari/Firefox can read it
- Results: refetch SCORM content when any part's revision changes; show a
  failed video as failed instead of "still rendering"

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/components/Toast.tsx

@@ -0,0 +1,28 @@
+// Short notices at the bottom of the screen (styles from the mockup's .toast), instead of alert().
+// A module-level store, so mutations can report from anywhere without a context provider.
+import { useSyncExternalStore } from 'react'
+
+interface Notice { id: number; text: string; error: boolean }
+
+let current: Notice | null = null
+let nextId = 1
+let timer: ReturnType<typeof setTimeout> | undefined
+const listeners = new Set<() => void>()
+const emit = () => listeners.forEach(l => l())
+
+export function toast(text: string, { error = false } = {}) {
+  current = { id: nextId++, text, error }
+  clearTimeout(timer)
+  // Errors stay a little longer: they usually need reading.
+  timer = setTimeout(() => { current = null; emit() }, error ? 7000 : 3500)
+  emit()
+}
+
+export function Toaster() {
+  const notice = useSyncExternalStore(cb => { listeners.add(cb); return () => listeners.delete(cb) }, () => current)
+  return (
+    <div className={`toast${notice ? ' show' : ''}${notice?.error ? ' error' : ''}`} role={notice?.error ? 'alert' : 'status'} aria-live="polite">
+      {notice?.text}
+    </div>
+  )
+}