Phase 1: scaffold + metronome engine + R1

Svelte 5 + Vite static SPA with absolute base and History-API path routing.
Core lookahead-scheduler metronome (no drift), AudioContext unlock-on-gesture,
synthesized 3-voice clicks, rAF-synced beat highlight. StrumGrid renderer and
R1 wired end-to-end with variants, BPM/variant persistence, query overrides,
and keyboard shortcuts (space, arrow up/down). Dark amp-light theme tokens.

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

src/pages/DrillPage.svelte

@@ -0,0 +1,23 @@
+<script lang="ts">
+  import { getDrill } from '../drills'
+  import NotFound from './NotFound.svelte'
+  import StrumView from '../components/views/StrumView.svelte'
+
+  interface Props {
+    code: string
+    params: URLSearchParams
+  }
+
+  let { code, params }: Props = $props()
+  let drill = $derived(getDrill(code))
+</script>
+
+{#if !drill}
+  <NotFound {code} />
+{:else if drill.kind === 'strum'}
+  {#key drill.code}
+    <StrumView {drill} {params} />
+  {/key}
+{:else}
+  <NotFound {code} />
+{/if}