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.

client/src/pages/Sessions.tsx

@@ -71,6 +71,7 @@ import { api } from "../lib/api";
 import type { RemoteSource, RunHandle } from "../lib/api";
 import { useLiveRefresh } from "../hooks/useLiveRefresh";
 import { laneChangeMatcher, runKeyOf } from "../lib/laneChange";
+import { useSpin } from "../hooks/useSpin";
 import { useAiTools } from "../hooks/useAiTools";
 import { useLanes } from "../hooks/useLanes";
 import { toast } from "../lib/toast";
@@ -238,6 +239,7 @@ export function Sessions({ embedded = false }: { embedded?: boolean } = {}) {
     // `scope` is a dep so a data-scope change re-fetches; the api layer injects
     // the matching `sources` param.
   }, [query, page, scope, t]);
+  const [spinning, refresh] = useSpin(load);
 
   useEffect(() => {
     load();
@@ -390,8 +392,9 @@ export function Sessions({ embedded = false }: { embedded?: boolean } = {}) {
           >
             <Download className="w-4 h-4" /> {t("exportJson")}
           </button>
-          <button onClick={load} className="btn-ghost">
-            <RefreshCw className="w-4 h-4" /> {t("common:refresh")}
+          <button onClick={refresh} disabled={spinning} aria-busy={spinning} className="btn-ghost">
+            <RefreshCw className={`w-4 h-4 ${spinning ? "animate-spin" : ""}`} />{" "}
+            {t("common:refresh")}
           </button>
         </div>
       </div>