Model graph: the whole model as one graph with queries; 0.9.0

- Model | Graph switch on main.archify (Diagram | Graph on diagram pages, narrowed to that diagram)
- union graph of every element and connection, registry and inline, built from the model index
- query box: text, type:, diagram:, decision:, uses:, near:, from: to:, unused, shared, -shared
- side panel per element and connection with diagrams, registry line and decisions one click away
- legend chips, Fit, Layout, Labels, Export PNG; Cytoscape.js bundled as dist/graph.js
- command Archify | Open Model Graph; integration check; unit tests for graph and queries

src/webview/host.ts

@@ -0,0 +1,20 @@
+import type { ModelGraph } from '../model/graph';
+
+/**
+ * What the bridge script (page.ts) exposes to the bundled page scripts as
+ * `window.__archifyHost`: they cannot call acquireVsCodeApi a second time.
+ */
+export interface ArchifyHost {
+  defaultView: '2d' | '3d';
+  post(message: unknown): void;
+  getState(): Record<string, unknown>;
+  setState(patch: Record<string, unknown>): void;
+  /** The Graph page's data, present on that page only. */
+  graph?: { graph: ModelGraph; query?: string };
+}
+
+declare global {
+  interface Window {
+    __archifyHost?: ArchifyHost;
+  }
+}