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/

src/vite-env.d.ts

@@ -7,3 +7,17 @@ declare module '*.module.css' {
   const classes: { readonly [key: string]: string };
   export default classes;
 }
+
+// The bundled Vega-Lite JSON schema is ~1.5 MB. Declaring it as a generic object
+// stops `tsc` from inferring a giant literal type (slow/memory-heavy) on import.
+declare module 'vega-lite/vega-lite-schema.json' {
+  const schema: Record<string, unknown>;
+  export default schema;
+}
+
+// `edcore.main` (full editor features, no bundled languages) ships no types of
+// its own; at runtime it re-exports the editor API, so map its types there.
+// This also re-pulls monaco's global `MonacoEnvironment` augmentation.
+declare module 'monaco-editor/esm/vs/editor/edcore.main' {
+  export * from 'monaco-editor/esm/vs/editor/editor.api';
+}