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/components/lanes/WorkspaceHome.tsx

@@ -202,6 +202,12 @@ function HomeBody({
   const [menuAt, setMenuAt] = useState<{ x: number; y: number } | null>(null);
   const [title, setTitle] = useState<string | null>(null);
   const fileInput = useRef<HTMLInputElement>(null);
+  const [ctxDrag, setCtxDrag] = useState(false);
+  const addFiles = async (picked: File[]) => {
+    for (const f of picked) {
+      if (!(await run(() => api.lanes.addFile(lane.id, f)))) break;
+    }
+  };
   const memoryPanel = useRef<HTMLDivElement>(null);
   useDialog(memoryOpen && !!memory, memoryPanel, () => setMemoryOpen(false));
   const recentCtx = useContextMenu<Session>();
@@ -328,7 +334,7 @@ function HomeBody({
         ...(claude && inWorktree && project?.root ? { worktree: true } : {}),
       });
       setPrompt("");
-      images.forEach((i) => URL.revokeObjectURL(i.url));
+      images.forEach((i) => i.url && URL.revokeObjectURL(i.url));
       setImages([]);
       navigate(`/workspace?lane=${lane.id}&run=${encodeURIComponent(runId)}`);
     } catch (err) {
@@ -839,7 +845,26 @@ function HomeBody({
           </p>
         </section>
 
-        <section className={card}>
+        <section
+          data-testid="workspace-context-files"
+          className={`${card} ${ctxDrag ? "ring-2 ring-accent/50" : ""}`}
+          // Files dragged in from the OS are added like the + button's pick.
+          onDragOver={(e) => {
+            if (!view || !e.dataTransfer.types.includes("Files")) return;
+            e.preventDefault();
+            e.dataTransfer.dropEffect = "copy";
+            setCtxDrag(true);
+          }}
+          onDragLeave={(e) => {
+            if (!e.currentTarget.contains(e.relatedTarget as Node | null)) setCtxDrag(false);
+          }}
+          onDrop={(e) => {
+            setCtxDrag(false);
+            if (!view || e.dataTransfer.files.length === 0) return;
+            e.preventDefault();
+            void addFiles([...e.dataTransfer.files]);
+          }}
+        >
           <div className="flex items-center justify-between">
             <h3 className="text-sm font-medium text-fg-primary">{t("home.context")}</h3>
             <button
@@ -858,12 +883,10 @@ function HomeBody({
               type="file"
               multiple
               hidden
-              onChange={async (e) => {
+              onChange={(e) => {
                 const picked = [...(e.target.files ?? [])];
                 e.target.value = "";
-                for (const f of picked) {
-                  if (!(await run(() => api.lanes.addFile(lane.id, f)))) break;
-                }
+                void addFiles(picked);
               }}
             />
           </div>