swarm-ui: page shell + layout primitives

Structural foundation split out of hyperhive#3118 per mara's steer:
structure first so the real overview page (hive roster) and later
routes (swarm-wide agent roster) land as content changes rather than
each reinventing chrome + nav + a table/panel/chip shape.

- <Shell>: header bar (branding) + nav row, wraps every route. Route
  list lives in Shell itself (one small SPA, one place to know its
  own nav).
- ui/Panel, ui/StatusChip, ui/Table: the three primitives the
  overview page's actual scope (hive roster: name/domain/status,
  linking out to each hive's own dashboard) calls for, nothing
  speculative beyond that.

Preact-native styling (plain CSS files imported via swarm-ui.css, no
shadow DOM — this package renders into light DOM) — not
@hive/shared's chrome.css, which is the old MPA dashboard's visual
language. Same base16/Catppuccin color tokens via theme.css/colors.css
so it still reads as hyperhive.

npm run build (whole frontend workspace) + npm run typecheck both
clean. Verified with a real headless-chromium screenshot against the
built dist, not just source-reading.

Fixes hyperhive#3211

frontend/packages/swarm-ui/src/App.tsx

@@ -1,35 +1,34 @@
-// Root shell component. Empty start page for now — functionality
-// (swarm roster, target-state view, whatever the swarm-controller
-// epic eventually needs) is out of scope until auth against authelia
-// is figured out. What's here IS in scope: a real router + deep-link
-// shape that the per-hive dashboard's vanilla-JS + custom-element MPA
-// doesn't have, so later work has a shell to land routes into instead
-// of bolting routing on after the fact.
+// Root shell component. Real route (`/`) is still a placeholder — the
+// swarm's hive roster is the next piece of work to land into it — but
+// it now mounts inside <Shell> and uses the ui/ primitives, so that
+// page lands as a content change, not a structural one.
 import { Route, Switch } from 'wouter-preact';
+import { Shell } from './shell/Shell.js';
+import { Panel } from './ui/Panel.js';
 
 function Home() {
   return (
-    <main class="swarm-ui-empty">
-      <h1>swarm ui</h1>
-      <p>nothing here yet — project-bootstrap placeholder.</p>
-    </main>
+    <Panel title="overview">
+      <p>hive roster lands here, sequenced after this shell.</p>
+    </Panel>
   );
 }
 
 function NotFound() {
   return (
-    <main class="swarm-ui-empty">
-      <h1>404</h1>
+    <Panel title="404">
       <p>no route here.</p>
-    </main>
+    </Panel>
   );
 }
 
 export function App() {
   return (
-    <Switch>
-      <Route path="/" component={Home} />
-      <Route component={NotFound} />
-    </Switch>
+    <Shell>
+      <Switch>
+        <Route path="/" component={Home} />
+        <Route component={NotFound} />
+      </Switch>
+    </Shell>
   );
 }