feat(hubs): Procurement / People / IT hubs over real EA2 catalogue

Single Hub component parameterised by hub key. Each hub:
- Lists quick actions that look up a matching published process and
  start it as a real transaction
- Pulls the full published catalogue from /api/ea2/flow/processes and
  filters via a hub-specific regex (procurement|hr|it)
- Falls back to top-N when no matches, with a Studio CTA when empty

Landing surface gets a hero-hub row of chips: Procurement Hub, People
Hub, IT Hub, Talk to Pi, Team Chat. Same EA2-write doctrine as wizard.

src/App.tsx

@@ -10,6 +10,7 @@ import Login from "./scenes/Login";
 import SsoCallback from "./scenes/SsoCallback";
 import Chat from "./scenes/Chat";
 import Agent from "./scenes/Agent";
+import Hub from "./scenes/Hub";
 import CommandBar from "./components/CommandBar";
 import Toaster from "./components/Toaster";
 import Console from "./components/Console";
@@ -159,6 +160,9 @@ export default function App() {
         {scene === "studio" && <Wizard />}
         {scene === "chat" && <Chat />}
         {scene === "agent" && <Agent />}
+        {scene === "hub-procurement" && <Hub hub="procurement" />}
+        {scene === "hub-hr" && <Hub hub="hr" />}
+        {scene === "hub-it" && <Hub hub="it" />}
         {scene === "settings" && <Settings />}
       </div>