feat(plot): Chunk #5 story whiteboard, timeline & plot beats

Story whiteboard built on React Flow v11: free-form canvas of typed
nodes (character, world, chapter, note, image, group) with draggable
leads-to/contrasts/causes edges, cross-link selectors (chapter/entity),
linked-node badges, and an "Add beats to board" import from the plot.

Plot beats feature set:
- Status/locking (draft/revised/locked) with a progress bar
- Beat templates (three-act, save-the-cat, seven-point, custom)
- Timeline route with search/chapter/character filters
- Entity cross-links (entityIds) on beats and board nodes
- getBoard added to the StorageAdapter contract (local + server) and
  REST endpoints; loadBoard now restores persisted board state

Storage & server:
- PlotBeat type (status, entityIds) across core types, Dexie schema,
  and server mapping/routes/migration (002_plot_beats.sql)
- SQLite-safe column names (beat_order, entity_ids)
- Server seed data for plot beats

UI: accent Button variant, Badge variants, plot/timeline/whiteboard
stylesheets. Tests: templates module, plot-beat store round-trip,
board getBoard. typecheck, lint, test, and build all green.

packages/core/src/storage-local.ts

@@ -7,6 +7,7 @@ import type {
   DocumentRef,
   Entity,
   NewProject,
+  PlotBeat,
   Project,
   ProjectMeta,
 } from "./types.js";
@@ -28,6 +29,7 @@ class PubScriptDB extends Dexie {
   chapters!: Table<Chapter, string>;
   entities!: Table<EntityRec, string>;
   boards!: Table<Board, string>;
+  plotBeats!: Table<PlotBeat, string>;
   aiSessions!: Table<AISession, string>;
 
   constructor() {
@@ -38,6 +40,8 @@ class PubScriptDB extends Dexie {
       chapters: "id, bookId, projectId",
       entities: "key, projectId, kind",
       boards: "id, projectId",
+      // Plot beats — atomic units of story structure (CHUNK #5).
+      plotBeats: "id, [projectId+act], projectId, chapterId",
       aiSessions: "id, projectId",
     });
   }
@@ -194,6 +198,35 @@ export const storageLocal: StorageAdapter = {
     await db.boards.put(b);
   },
 
+  async getBoard(projectId: string): Promise<Board | null> {
+    const rows = await db.boards
+      .where("projectId")
+      .equals(projectId)
+      .toArray();
+    return rows[0] ?? null;
+  },
+
+  async listPlotBeats(projectId: string): Promise<PlotBeat[]> {
+    const rows = await db.plotBeats
+      .where("projectId")
+      .equals(projectId)
+      .toArray();
+    // Stable order: by act, then order within act.
+    return rows.sort((a, b) => a.act - b.act || a.order - b.order);
+  },
+
+  async savePlotBeat(b: PlotBeat): Promise<void> {
+    await db.plotBeats.put(b);
+  },
+
+  async deletePlotBeat(projectId: string, id: string): Promise<void> {
+    const existing = await db.plotBeats.get(id);
+    if (!existing || existing.projectId !== projectId) {
+      throw new Error(`No plot beat ${id} in project ${projectId}.`);
+    }
+    await db.plotBeats.delete(id);
+  },
+
   async saveAISession(s: AISession): Promise<void> {
     await db.aiSessions.put(s);
   },