dashboard: extract themed dialog into a reusable modal.js component

Move the themed dialog out of common.js into its own modal.js module: a
general openDialog(title/message/content/buttons) primitive with themedConfirm
as a thin cancel/confirm wrapper on top. tabs.js imports it from there. No
behaviour change to the stop-confirm flow; the dialog is now a standalone
reusable component other surfaces can open.

frontend/packages/dashboard/src/dashboard.css

@@ -414,6 +414,59 @@ body.dashboard-shell {
 }
 .container-row .actions form.inline { display: inline-block; margin: 0; }
 
+/* Themed confirm modal — `themedConfirm()` in common.js. In-theme replacement
+   for the native confirm() on destructive actions (stop / restart / destroy),
+   carrying the optional "stop gracefully" checkbox. */
+.tc-backdrop {
+  position: fixed;
+  inset: 0;
+  z-index: 1000;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  padding: 1em;
+  background: color-mix(in srgb, var(--crust) 60%, transparent);
+  -webkit-backdrop-filter: blur(2px);
+  backdrop-filter: blur(2px);
+}
+.tc-box {
+  background: var(--bg-elev);
+  border: 1px solid var(--purple-dim);
+  box-shadow: 0 8px 40px -8px var(--crust);
+  padding: 1.2em 1.4em;
+  max-width: min(32em, 92vw);
+  display: flex;
+  flex-direction: column;
+  gap: 0.9em;
+}
+.tc-title {
+  font-weight: bold;
+  text-transform: uppercase;
+  letter-spacing: 0.08em;
+  color: var(--subtext0);
+}
+.tc-message { color: var(--fg); line-height: 1.45; }
+.tc-checks { display: flex; flex-direction: column; gap: 0.4em; }
+.tc-checkrow {
+  display: flex;
+  align-items: flex-start;
+  gap: 0.5em;
+  cursor: pointer;
+  color: var(--subtext0);
+  font-size: 0.92em;
+  line-height: 1.35;
+}
+.tc-checkrow .tc-check { margin-top: 0.2em; flex: 0 0 auto; }
+.tc-actions {
+  display: flex;
+  justify-content: flex-end;
+  gap: 0.6em;
+  margin-top: 0.2em;
+}
+.tc-cancel { color: var(--subtext0); }
+.tc-confirm { color: var(--green); }
+.tc-confirm.tc-danger { color: var(--red); }
+
 .agent-status {
   font-size: 0.82em;
   color: var(--subtext0);

frontend/packages/dashboard/src/modal.js

@@ -0,0 +1,115 @@
+// modal.js — reusable themed modal/dialog component for the operator
+// dashboard. An in-theme replacement for the browser's native
+// `confirm()` / `alert()` overlays so destructive actions and prompts match
+// the dashboard chrome instead of a jarring OS dialog.
+//
+// `openDialog` is the general primitive (any title/message/content + a row of
+// buttons); `themedConfirm` is a thin cancel/confirm wrapper with optional
+// checkboxes built on top of it. Styling lives in `dashboard.css` under the
+// `.tc-*` classes.
+
+import { el } from './common.js';
+
+// openDialog({ title, message, content, buttons, danger, dismissable })
+//   → Promise resolving to the clicked button's `value`, or `null` when the
+//     dialog is dismissed (Escape, backdrop click, or a button whose value is
+//     null). `content` is an optional DOM node rendered between the message
+//     and the buttons (checkboxes, custom fields, …). `buttons` is
+//     `[{ label, value, danger?, class?, autofocus? }]`, rendered
+//     right-aligned. Initial focus: the `autofocus` button if any, else — for
+//     a `danger` dialog — the first non-destructive button (so a stray Enter
+//     can't fire the destructive path), else the last button.
+export function openDialog(opts = {}) {
+  const {
+    title = '', message = '', content = null,
+    buttons = [{ label: 'ok', value: true }],
+    danger = false, dismissable = true,
+  } = opts;
+
+  return new Promise((resolve) => {
+    let settled = false;
+    function done(value) {
+      if (settled) return;
+      settled = true;
+      document.removeEventListener('keydown', onKey, true);
+      backdrop.remove();
+      resolve(value);
+    }
+    function onKey(e) {
+      if (dismissable && e.key === 'Escape') {
+        e.preventDefault();
+        e.stopPropagation();
+        done(null);
+      }
+    }
+
+    const btnEls = buttons.map((b) => {
+      const btn = el('button', {
+        type: 'button',
+        class: 'btn tc-btn' + (b.class ? ' ' + b.class : '') + (b.danger ? ' tc-danger' : ''),
+      }, b.label);
+      btn.addEventListener('click', () => done(b.value));
+      return { spec: b, btn };
+    });
+
+    const box = el('div', { class: 'tc-box', role: 'dialog', 'aria-modal': 'true' },
+      title ? el('div', { class: 'tc-title' }, title) : null,
+      message ? el('div', { class: 'tc-message' }, message) : null,
+      content || null,
+      el('div', { class: 'tc-actions' }, ...btnEls.map((b) => b.btn)));
+
+    const backdrop = el('div', { class: 'tc-backdrop' }, box);
+    backdrop.addEventListener('click', (e) => {
+      if (dismissable && e.target === backdrop) done(null);
+    });
+    document.addEventListener('keydown', onKey, true);
+    document.body.append(backdrop);
+
+    const focusTarget = btnEls.find((b) => b.spec.autofocus)
+      || (danger ? btnEls.find((b) => !b.spec.danger) : null)
+      || btnEls[btnEls.length - 1];
+    if (focusTarget) focusTarget.btn.focus();
+  });
+}
+
+// themedConfirm({ title, message, danger, confirmLabel, cancelLabel, checkboxes })
+//   → Promise<null | { [name]: bool }>. `null` = cancelled; otherwise an
+//   object of the checkbox states keyed by `name` (`{}` when there are none).
+//   Example:
+//     const r = await themedConfirm({ message: `stop ${n}?`, danger: true,
+//       confirmLabel: '■ stop', checkboxes: [{ name: 'graceful', label: '…' }] });
+//     if (!r) return;            // cancelled
+//     doStop(r.graceful);
+export function themedConfirm(opts = {}) {
+  const {
+    title = '', message = '', danger = false,
+    confirmLabel = 'confirm', cancelLabel = 'cancel', checkboxes = [],
+  } = opts;
+
+  const boxes = checkboxes.map((cb) => {
+    const input = el('input', { type: 'checkbox', class: 'tc-check', name: cb.name });
+    if (cb.checked) input.checked = true;
+    const row = el('label', { class: 'tc-checkrow' },
+      input, el('span', { class: 'tc-check-label' }, cb.label || cb.name));
+    return { input, row };
+  });
+  const content = boxes.length
+    ? el('div', { class: 'tc-checks' }, ...boxes.map((b) => b.row))
+    : null;
+
+  return openDialog({
+    title,
+    message,
+    content,
+    danger,
+    buttons: [
+      { label: cancelLabel, value: null, class: 'tc-cancel', autofocus: danger },
+      { label: confirmLabel, value: 'confirm', danger, class: 'tc-confirm', autofocus: !danger },
+    ],
+  }).then((v) => {
+    if (v !== 'confirm') return null;
+    const out = {};
+    for (let i = 0; i < boxes.length; i++) out[checkboxes[i].name] = boxes[i].input.checked;
+    return out;
+  });
+}

frontend/packages/dashboard/src/tabs.js

@@ -18,6 +18,7 @@ import {
   makePathLink, appendText, appendLinkified,
   openStream, renderServerWarnings, bindAsyncForms,
 } from './common.js';
+import { themedConfirm } from './modal.js';
 import { createTabStrip } from '@hive/shared/tabs.js';
 import {
   containersState, syncContainersFromSnapshot,
@@ -281,8 +282,8 @@ window.marked = marked;
   }, true);
 
   // Single-agent POST helper shared by all menu items.
-  async function agentMenuPost(actionPath, name, body) {
-    const url = actionPath + encodeURIComponent(name);
+  async function agentMenuPost(actionPath, name, body, graceful) {
+    const url = actionPath + encodeURIComponent(name) + (graceful ? '?graceful=1' : '');
     try {
       const resp = await fetch(url, {
         method: 'POST',
@@ -323,8 +324,20 @@ window.marked = marked;
       }, label);
       item.addEventListener('click', async () => {
         closeAllAgentMenus();
-        if (opts.confirm && !confirm(opts.confirm)) return;
-        await agentMenuPost(opts.action, c.name, opts.body || null);
+        let graceful = false;
+        if (opts.confirm) {
+          const r = await themedConfirm({
+            message: opts.confirm,
+            danger: true,
+            confirmLabel: opts.confirmLabel || 'confirm',
+            checkboxes: opts.graceful
+              ? [{ name: 'graceful', label: 'stop gracefully — let the agent finish its turn and flush state before the container stops' }]
+              : [],
+          });
+          if (!r) return;
+          graceful = !!r.graceful;
+        }
+        await agentMenuPost(opts.action, c.name, opts.body || null, graceful);
       });
       li.append(item);
       return li;
@@ -352,7 +365,7 @@ window.marked = marked;
     if (c.running) {
       dropdown.append(
         menuItem('↺ R3ST4RT', { action: '/restart/', confirm: `restart ${c.name}?` }),
-        menuItem('■ ST0P', { action: '/kill/', confirm: `stop ${c.name}?` }),
+        menuItem('■ ST0P', { action: '/kill/', confirm: `stop ${c.name}?`, confirmLabel: '■ stop', graceful: true }),
       );
     } else {
       dropdown.append(
@@ -982,6 +995,8 @@ window.marked = marked;
     addBulkButton(actions, 'btn-stop', '■ ST0P', allRunning, selected, {
       action: '/kill/',
       confirm: (names) => `stop ${names.length} agent${names.length === 1 ? '' : 's'} (${names.join(', ')})?`,
+      confirmLabel: '■ stop',
+      graceful: true,
       disabledTitle: why('■ ST0P', stoppedNames.map((n) => `\`${n}\` is already stopped`)),
     });
     addBulkButton(actions, 'btn-start', '▶ ST4RT', allStopped, selected, {
@@ -1145,7 +1160,19 @@ window.marked = marked;
     btn.addEventListener('click', async () => {
       if (btn.disabled) return;
       const msg = opts.confirm(names);
-      if (msg && !confirm(msg)) return;
+      let graceful = false;
+      if (msg) {
+        const r = await themedConfirm({
+          message: msg,
+          danger: true,
+          confirmLabel: opts.confirmLabel || 'confirm',
+          checkboxes: opts.graceful
+            ? [{ name: 'graceful', label: 'stop gracefully — let each agent finish its turn and flush state before the container stops' }]
+            : [],
+        });
+        if (!r) return;
+        graceful = !!r.graceful;
+      }
       btn.disabled = true;
       const original = btn.innerHTML;
       btn.innerHTML = '<span class="spinner">◐</span> ' + label;
@@ -1168,7 +1195,7 @@ window.marked = marked;
           : new URLSearchParams(opts.body || {});
         const url = opts.perAgentBodyFor
           ? opts.action
-          : opts.action + encodeURIComponent(name);
+          : opts.action + encodeURIComponent(name) + (graceful ? '?graceful=1' : '');
         try {
           const resp = await fetch(url, {
             method: 'POST',