agent: wire Header/StatusChips to real /api/state polling

- useAgentState hook: polls GET /api/state (4s interval for now — see
  its file comment for why this isn't yet the SSE-triggered + login-
  only-timer cadence the old page used; that lands with the live
  stream + term-input commit, which is when clobbering the operator's
  in-progress input actually becomes a risk).
- format.ts: fmtTokens/fmtAge, same output shapes as app.js's.
- modelEffort.ts: POST /api/model + /api/effort (same-origin, plain
  fetch).
- dashboardBase.ts + pauseAction.ts: pause/resume POST to the
  *dashboard's* origin via a real <form> submit, kept unchanged from
  app.js — a cross-origin fetch needs CORS headers hive-c0re doesn't
  send, a form submit sidesteps that same as it already did.
- Root.tsx: wires it all together, including app.js's "any non-online
  status forces the turn-state badge to offline" behavior.

Screenshot-verified against a mock GET /api/state (real fetch, not
hardcoded props) + the real agent.css/theme.css/colors.css.

Builds + tsc --noEmit clean.

frontend/packages/agent/src/lib/dashboardBase.ts

@@ -0,0 +1,11 @@
+// Resolves the host dashboard's origin, ported unchanged from app.js's
+// `setHeader` — pause/resume are host-side (hive-c0re) actions, not
+// this agent's own `/api/*`, so they need the *dashboard's* origin, not
+// a relative path. Behind the gateway this page lives at
+// `/agent/<name>/` on the dashboard's own origin (`location.origin`);
+// accessed directly, it's the same host on `dashboardPort`.
+export function resolveDashboardBase(dashboardPort: number): string {
+  return location.pathname.startsWith('/agent/')
+    ? location.origin + '/'
+    : `${location.protocol}//${location.hostname}:${dashboardPort}/`;
+}