feat(switcher): per-workspace device count in dropdown rows

/me's accessible_workspaces query gains a device_count field via a
correlated subquery on workspaces.id - WHERE workspace_id = w.id
strictly excludes the unclaimed pair-pool (workspace_id IS NULL fails
equality). Added to both query branches (platform_admin LEFT JOIN and
regular INNER JOIN); microseconds per row at current scale (~37 rows
worst case), not optimizing.

Frontend appends the count to the muted org-name line with a middle-dot
separator: 'Acme Studios . 2 devices'. Singular/plural respected via the
existing tn() helper convention; 'No devices' for empty workspaces. New
formatResourceCount(n, keyBase, zeroKey) helper is generic so the same
shape can wire users/playlists/schedules counts later without refactor.

New i18n keys: switcher.devices_count_one, switcher.devices_count_other,
switcher.no_devices. Added to en.js only; other locales fall back to en
via the existing lookup chain (verified in i18n.js:19).

API smoke verified: switcher-test sees Studio A=2, Field Crew=2;
dw5304 (platform_admin) sees all 37 workspaces with their device counts
varying 0-4; single-workspace zero-device user (geoff.case) sees 0.

frontend/js/components/workspace-switcher.js

@@ -1,5 +1,18 @@
 import { api } from '../api.js';
 import { showToast } from './toast.js';
+import { t, tn } from '../i18n.js';
+
+// Reusable resource-count formatter. Returns localized "1 device" / "N devices"
+// / "No devices" based on n. Generic so the same shape can wire users /
+// playlists / schedules counts later without refactor - caller supplies the
+// i18n key bases.
+//   keyBase: e.g. 'switcher.devices_count' (looks up _one / _other variants via tn)
+//   zeroKey: e.g. 'switcher.no_devices' (direct lookup for n === 0)
+function formatResourceCount(n, keyBase, zeroKey) {
+  if (n === undefined || n === null) return '';
+  if (n === 0) return t(zeroKey);
+  return tn(keyBase, n);
+}
 
 // Render the workspace switcher inside #workspaceSwitcher based on the
 // /api/auth/me response. Three modes:
@@ -37,14 +50,21 @@ export function renderWorkspaceSwitcher(me) {
       </svg>
     </button>
     <div class="workspace-switcher-menu" role="listbox">
-      ${sorted.map(w => `
+      ${sorted.map(w => {
+        const countStr = formatResourceCount(w.device_count, 'switcher.devices_count', 'switcher.no_devices');
+        const orgName = w.organization_name || '';
+        const subtitle = orgName && countStr ? esc(orgName) + ' · ' + esc(countStr)
+                       : orgName            ? esc(orgName)
+                       : countStr           ? esc(countStr)
+                                            : '';
+        return `
         <div class="workspace-switcher-item ${w.id === currentId ? 'current' : ''}" data-workspace-id="${esc(w.id)}" role="option">
           <svg class="check" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="3" style="${w.id === currentId ? '' : 'visibility:hidden'}">
             <polyline points="20 6 9 17 4 12"/>
           </svg>
           <div class="ws-meta">
             <div class="ws-name">${esc(w.name)}</div>
-            <div class="ws-org">${esc(w.organization_name || '')}</div>
+            <div class="ws-org">${subtitle}</div>
           </div>
           ${w.can_admin ? `
             <button class="workspace-switcher-pencil" type="button" data-rename-id="${esc(w.id)}" aria-label="Rename workspace" title="Rename">
@@ -54,7 +74,8 @@ export function renderWorkspaceSwitcher(me) {
             </button>
           ` : ''}
         </div>
-      `).join('')}
+      `;
+      }).join('')}
     </div>
   `;
 

frontend/js/i18n/en.js

@@ -1105,4 +1105,10 @@ export default {
   'add_display.windows': 'Windows',
   'add_display.smart_tv_note': 'Smart TVs (LG/Samsung): open the built-in browser and navigate to <code style="background:var(--bg-input,#0f172a);padding:1px 4px;border-radius:3px">/player</code>',
   'add_display.pair_btn': 'Pair Display',
+
+  // Workspace switcher (Phase 3 MVP). devices_count is the only count exposed
+  // today; matching pattern for users/playlists/etc. when those land later.
+  'switcher.devices_count_one': '1 device',
+  'switcher.devices_count_other': '{n} devices',
+  'switcher.no_devices': 'No devices',
 };

server/routes/auth.js

@@ -305,11 +305,16 @@ router.get('/me', requireAuth, resolveTenancy, (req, res) => {
   // UI can render admin affordances (rename pencil etc.) only where the
   // caller has permission. The server still enforces permission on the
   // actual mutation routes regardless of this advisory flag.
+  // device_count: correlated subquery on workspaces.id. Equality fails on NULL
+  // so unclaimed pair-pool devices (workspace_id IS NULL) are correctly excluded.
+  // Microseconds per row at current scale (~37 rows worst case for platform_admin);
+  // not optimizing - revisit if the admin list grows past a few hundred workspaces.
   const isPlatformAdmin = req.user.role === 'platform_admin' || req.user.role === 'superadmin';
   const accessible = isPlatformAdmin
     ? db.prepare(`
         SELECT w.id, w.name, w.organization_id, o.name AS organization_name,
-               wm.role AS workspace_role, om.role AS org_role
+               wm.role AS workspace_role, om.role AS org_role,
+               (SELECT COUNT(*) FROM devices WHERE workspace_id = w.id) AS device_count
         FROM workspaces w
         JOIN organizations o ON o.id = w.organization_id
         LEFT JOIN workspace_members wm ON wm.workspace_id = w.id AND wm.user_id = ?
@@ -318,7 +323,8 @@ router.get('/me', requireAuth, resolveTenancy, (req, res) => {
       `).all(req.user.id, req.user.id)
     : db.prepare(`
         SELECT w.id, w.name, w.organization_id, o.name AS organization_name,
-               wm.role AS workspace_role, om.role AS org_role
+               wm.role AS workspace_role, om.role AS org_role,
+               (SELECT COUNT(*) FROM devices WHERE workspace_id = w.id) AS device_count
         FROM workspace_members wm
         JOIN workspaces w ON w.id = wm.workspace_id
         JOIN organizations o ON o.id = w.organization_id