feat: persist presentation figure focus

- Add focusPath to MainLocation and FigureBeatDefinition to SceneBeatDefinition
- Canonical hash format: #scene/<scene>/<beat>/focus/<segment>/<segment>
- Add set_focus_path reducer action
- Next/previous restores destination beat's canonical Focus Path
- Discussion return preserves exact originating Focus Path
- Fix catalog cycle detection to cover disconnected subgraphs
- Add FigureCatalogIssue typed issue model
- Fix test fixtures using nonexistent edge endpoints
- Remove unsafe non-null assertions in catalog and focus modules

web/apps/console/src/presentation/storyboard.test.ts

@@ -59,7 +59,7 @@ describe("defense storyboard catalog", () => {
   });
 
   it("exposes a valid default location", () => {
-    expect(defaultMainLocation).toEqual({ kind: "main", sceneId: "thesis", beatId: "title" });
+    expect(defaultMainLocation).toEqual({ kind: "main", sceneId: "thesis", beatId: "title", focusPath: [] });
     expect(findScene(defaultMainLocation.sceneId)?.number).toBe(1);
   });
 });