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/app/services/chart-renderer.ts

@@ -0,0 +1,37 @@
+/**
+ * Chart renderer (docs/architecture/05 §2).
+ *
+ * The one place in the app that touches `vega-embed` and the chart DOM.
+ * Components ask it to draw a prepared spec into a node and own the returned
+ * handle's lifecycle: every successful embed yields a live Vega `View` that must
+ * be finalized before the next embed (or it leaks timers, listeners, and DOM).
+ */
+
+import vegaEmbed, { type Result as EmbedResult } from 'vega-embed';
+import type { VisualizationSpec } from 'vega-embed';
+import type { Config } from 'vega-lite';
+
+export interface RenderHandle {
+  /** Finalize the underlying Vega view and clear the node. */
+  destroy(): void;
+}
+
+/** Embed a prepared spec into `node`. Non-negotiable: no actions menu, SVG output. */
+export async function renderSpec(
+  node: HTMLElement,
+  spec: VisualizationSpec,
+  config: Config,
+): Promise<RenderHandle> {
+  const result: EmbedResult = await vegaEmbed(node, spec, {
+    actions: false, // Astrolabe owns its own export/copy affordances
+    renderer: 'svg',
+    config,
+  });
+
+  return {
+    destroy() {
+      result.view.finalize();
+      node.replaceChildren();
+    },
+  };
+}