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/format.ts

@@ -0,0 +1,17 @@
+// Formatting helpers ported from app.js's `fmtTokens`/`fmtAge` (same
+// output shapes — this page's operators are used to reading them).
+
+export function fmtTokens(n: number): string {
+  if (n >= 1_000_000) return (n / 1_000_000).toFixed(1) + 'M';
+  if (n >= 1_000) return Math.round(n / 1000) + 'k';
+  return String(n);
+}
+
+export function fmtAge(ms: number): string {
+  const s = Math.floor(ms / 1000);
+  if (s < 60) return s + 's';
+  const m = Math.floor(s / 60);
+  if (m < 60) return m + 'm ' + (s % 60) + 's';
+  const h = Math.floor(m / 60);
+  return h + 'h ' + (m % 60) + 'm';
+}