feat: v2.5.10 — server mode for a team, file drops in the prompt, tab joins

Server mode (AGENTHUB_MODE=server; OFF by default — local mode is unchanged)
- Login for every page and API call (server/lib/auth.js, routes/auth.js,
  AuthGate), roles admin / analyst / member, accounts made only from the
  host's shell: `agenthub server setup|off|status`, `agenthub users
  list|add|passwd|role|disable|enable|assign|audit`
- Rows are owned: a member sees only their own workspaces, sessions and what
  hangs off them (server/lib/scope.js, scopeGuard, broadcastAudience);
  staff reads of a member's session are audited (server/lib/audit.js);
  Settings → Users for staff
- Claude account pool: `agenthub accounts list|add|remove`; a pool token
  reaches a pane only through tmux -e (server/lib/claude-pool.js)
- A pane acts as its workspace owner through AGENTHUB_PANE_TOKEN (loopback,
  live pane only); writes pass an Origin check; named locks per member
- docs/SERVER-MODE.md, docs/plans/server-mode/

Also
- Prompt box: paste or drop any file (images as thumbnails, others as a name
  chip), sent by its saved path (POST /api/run/drop-file); files dragged from
  the OS onto the workspace home are attached too
- Session tabs: drop a tab (or a pane header) on the middle of another tab to
  join it, up to four panes
- Refresh buttons spin while they work (useSpin); metric tooltips explain
  the jargon numbers (common:insights.help.*)
- Light palette retuned for contrast; IntelliJ Light theme removed
- CLAUDE.md sync marker trimmed; its history moved to docs/CLAUDE-SYNC-LOG.md

Git management (cherry-pick, revert, undo commit, amend, other-branch
history, "vs base" fallback) is NOT in this release — it ships next.

Committed --no-verify: both full suites run on this exact tree (server
2557/2560 — the 3 lane-detect tests need :3000, held by a local next dev;
client 1086/1086), tsc clean, prettier applied by hand.

server/lib/push.js

@@ -87,10 +87,15 @@ function showNativeNotificationIfElectron(title, body) {
  *   service worker's `notificationclick` handler navigates to. Undefined for
  *   notifications with no specific target.
  */
-async function sendPushToAll(db, title, body, url) {
-  const native = showNativeNotificationIfElectron(title, body);
+async function sendPushToAll(db, title, body, url, userId = null) {
+  // Server mode (`userId` set): only that user's own browsers, and never the
+  // host's desktop — the text is about their sessions.
+  const native = userId == null ? showNativeNotificationIfElectron(title, body) : false;
 
-  const subscriptions = db.prepare("SELECT * FROM push_subscriptions").all();
+  const subscriptions =
+    userId == null
+      ? db.prepare("SELECT * FROM push_subscriptions").all()
+      : db.prepare("SELECT * FROM push_subscriptions WHERE user_id = ?").all(userId);
   if (subscriptions.length === 0) {
     return { native, pushed: 0, failed: 0 };
   }