fix(dashboard): wire data-async form submit handler on the C0R3 page

Clicking "update & rebuild" (and cancel / respawn / purge) on /core.html
navigated to the bare `ok` response page instead of submitting async. The
C0R3 page (split out of the dashboard) carries `data-async` forms but its
bundle never had the global submit interceptor — that handler lived inline
in tabs.js, so only the dashboard bundle had it. The forms POSTed natively
and the browser followed the response.

Fix: lift the `data-async` submit handler out of tabs.js into a shared
`bindAsyncForms(onSuccess)` in common.js (which already owns the `form`
helper that builds these forms), and call it from both pages:
- tabs.js: `bindAsyncForms(() => refreshState())` — behaviour-preserving
  (same handler, now imported).
- core.js: add a `refreshState()` (re-fetch /api/state + re-render) used
  for the cold load and as the post-submit refresh, and call
  `bindAsyncForms(() => refreshState())` at boot.

Forms with `data-no-refresh` (e.g. meta-update, which gets its update via
the meta SSE events) skip the refresh, same as before.

frontend/packages/dashboard/src/tabs.js

@@ -16,7 +16,7 @@ import {
   fmtAgeSecs,
   Panel, NOTIF,
   makePathLink, appendText, appendLinkified,
-  openStream, renderServerWarnings,
+  openStream, renderServerWarnings, bindAsyncForms,
 } from './common.js';
 import { createTabStrip } from '@hive/shared/tabs.js';
 import { containersState, syncContainersFromSnapshot } from './state.js';
@@ -90,64 +90,10 @@ window.marked = marked;
   }
 
   // ─── async forms ────────────────────────────────────────────────────────
-  document.addEventListener('submit', async (e) => {
-    const f = e.target;
-    if (!(f instanceof HTMLFormElement) || !f.hasAttribute('data-async')) return;
-    e.preventDefault();
-    if (f.dataset.confirm && !confirm(f.dataset.confirm)) return;
-    if (f.dataset.prompt) {
-      const ans = prompt(f.dataset.prompt, '');
-      if (ans === null) return;  // operator hit Cancel
-      // Drop into a hidden input named after `data-prompt-field` (or
-      // 'note' by default) so the value rides along on the POST.
-      const field = f.dataset.promptField || 'note';
-      let input = f.querySelector(`input[name="${field}"]`);
-      if (!input) {
-        input = document.createElement('input');
-        input.type = 'hidden';
-        input.name = field;
-        f.append(input);
-      }
-      input.value = ans;
-    }
-    const btn = f.querySelector('button[type="submit"], button:not([type]), .btn-inline');
-    const original = btn ? btn.innerHTML : '';
-    if (btn) { btn.disabled = true; btn.innerHTML = '<span class="spinner">◐</span>'; }
-    try {
-      const resp = await fetch(f.action, {
-        method: f.method || 'POST',
-        headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
-        body: new URLSearchParams(new FormData(f)),
-        redirect: 'manual',
-      });
-      const ok = resp.ok || resp.type === 'opaqueredirect'
-        || (resp.status >= 200 && resp.status < 400);
-      if (!ok) {
-        const text = await resp.text().catch(() => '');
-        alert('action failed: ' + resp.status + (text ? '\n\n' + text : ''));
-        if (btn) { btn.disabled = false; btn.innerHTML = original; }
-        return;
-      }
-      // Re-enable the button — refreshState() rebuilds most lists but
-      // skips forms that didn't change (e.g. the spawn form), so without
-      // this the spinner sticks and the button can't be clicked again.
-      if (btn) { btn.disabled = false; btn.innerHTML = original; }
-      // Clear text inputs whose value was just submitted.
-      f.querySelectorAll('input[type="text"], input:not([type]), textarea').forEach((i) => { i.value = ''; });
-      // Forms whose endpoint already emits a DashboardEvent that
-      // updates the derived store can opt out of the post-submit
-      // /api/state refetch (the event delivers the new row faster
-      // than the snapshot poll anyway). Container-lifecycle forms
-      // still rely on the refresh since `ContainerView` isn't yet
-      // event-derivable.
-      if (!f.hasAttribute('data-no-refresh')) {
-        refreshState();
-      }
-    } catch (err) {
-      alert('action failed: ' + err);
-      if (btn) { btn.disabled = false; btn.innerHTML = original; }
-    }
-  });
+  // Shared `data-async` submit interceptor (now in common.js so /core.html's
+  // bundle gets it too). On success it re-runs refreshState unless the form
+  // opts out via `data-no-refresh` (its mutation arrives via an SSE event).
+  bindAsyncForms(() => refreshState());
 
   // The live agent roster (`containersState`) + its snapshot-sync now
   // live in `./state.js` — it's the one piece of cross-domain state, read