feat(blocks): add reusable application shell blocks

- add appearance state, theme presets, preference controls, and preview components

- add responsive primary, nested, mobile, and flyout navigation with route-aware breadcrumbs

- add application layout, sidebar state, header actions, user menu, query refresh, and scroll utilities

- add configurable chat and notification surfaces backed by consumer-provided data and queries

- expose package entry points and cover theme, state, and command behavior with tests

packages/blocks/src/lib/command-actions.test.tsx

@@ -0,0 +1,35 @@
+// @vitest-environment jsdom
+
+import { fireEvent, render } from "@testing-library/react"
+import { describe, expect, it, vi } from "vitest"
+import {
+  getNavigationCommandProps,
+  NavigationActionTarget,
+  navigationActions,
+} from "./command-actions"
+
+describe("navigation command", () => {
+  it("connects an action button to its command target", () => {
+    expect(getNavigationCommandProps(navigationActions.search)).toEqual({
+      command: "--invoke",
+      commandfor: "navigation-action-search",
+    })
+  })
+
+  it("invokes the matching command target", () => {
+    const onInvoke = vi.fn()
+    const { container } = render(
+      <NavigationActionTarget
+        action={navigationActions.search}
+        onInvoke={onInvoke}
+      />
+    )
+    const target = container.querySelector("#navigation-action-search")
+    const event = new Event("command")
+    Object.defineProperty(event, "command", { value: "--invoke" })
+
+    fireEvent(target!, event)
+
+    expect(onInvoke).toHaveBeenCalledOnce()
+  })
+})