Implement M1 authoring loop: library, editor, live preview, persistence

M1 MVP from docs/IMPLEMENTATION-PLAN.md, with the /alignment pass applied.

- core: Snippet model + factory; prepareSpecForRender (copy-not-mutate); per-theme Vega chart config
- state/orchestration: SnippetStore with debounced auto-save; IndexedDB adapter + read-time migration; startup hydration + write-through persistence
- ui: SnippetLibrary, SpecEditor (Monaco edcore.main — full editor features, JSON-only languages), LivePreview
- build: Monaco/Vega manual chunks; raised PWA precache ceiling
- alignment: flush a valid draft on snippet switch (+regression tests); TODO breadcrumbs for the preview render race and the window.confirm delete
- housekeeping: gitignore .claude/projects/

vite.config.ts

@@ -16,6 +16,19 @@ export default defineConfig({
   define: {
     __APP_VERSION__: JSON.stringify(pkg.version),
   },
+  build: {
+    rollupOptions: {
+      output: {
+        // Split the heavy vendors so the chunk graph stays legible and the PWA
+        // can precache/update them independently of app code. Monaco and the
+        // Vega stack are each multi-MB; isolating them keeps app rebuilds small.
+        manualChunks: {
+          monaco: ['monaco-editor'],
+          vega: ['vega', 'vega-lite', 'vega-embed'],
+        },
+      },
+    },
+  },
   plugins: [
     react(),
     VitePWA({
@@ -30,6 +43,11 @@ export default defineConfig({
         display: 'standalone',
         icons: [],
       },
+      workbox: {
+        // Monaco and Vega vendor chunks exceed Workbox's 2 MiB default; raise the
+        // ceiling so the whole app (offline is a core requirement) is precached.
+        maximumFileSizeToCacheInBytes: 6 * 1024 * 1024,
+      },
     }),
   ],
   // Vitest config (shares this file)