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/SessionOverview.tsx

@@ -88,12 +88,15 @@ function StatTile({
   label,
   value,
   hint,
+  help,
   icon,
   tone = "default",
 }: {
   label: string;
   value: React.ReactNode;
   hint?: string;
+  /** Plain-language explanation, shown as the label's tooltip. */
+  help?: string;
   icon: React.ReactNode;
   tone?: "default" | "violet" | "emerald" | "amber" | "rose" | "cyan" | "blue";
 }) {
@@ -120,9 +123,14 @@ function StatTile({
 
   return (
     <div className={`rounded-lg border px-3 py-2.5 ${palette}`}>
-      <div className="flex items-center gap-1.5 text-[10px] uppercase tracking-wider text-fg-muted">
+      <div
+        className={`flex items-center gap-1.5 text-[10px] uppercase tracking-wider text-fg-muted${help ? " cursor-help" : ""}`}
+        title={help}
+      >
         <span className={iconTone}>{icon}</span>
-        {label}
+        <span className={help ? "underline decoration-dotted underline-offset-2" : undefined}>
+          {label}
+        </span>
       </div>
       <div className="mt-1 font-mono text-lg font-semibold text-fg-primary leading-tight">
         {value}
@@ -310,6 +318,7 @@ export function SessionOverview({ session, agents, stats: frozen }: SessionOverv
       <div className="grid grid-cols-2 sm:grid-cols-3 lg:grid-cols-6 gap-2.5">
         <StatTile
           label={t("overview.events")}
+          help={t("common:insights.help.events")}
           value={stats.total_events.toLocaleString()}
           hint={
             eventRate !== null && eventRate > 0
@@ -322,6 +331,7 @@ export function SessionOverview({ session, agents, stats: frozen }: SessionOverv
         />
         <StatTile
           label={t("overview.toolCalls")}
+          help={t("common:insights.help.toolCalls")}
           value={toolCallCount.toLocaleString()}
           hint={distinctTools > 0 ? t("overview.unique", { count: distinctTools }) : undefined}
           icon={<Wrench className="w-3 h-3" />}
@@ -329,6 +339,7 @@ export function SessionOverview({ session, agents, stats: frozen }: SessionOverv
         />
         <StatTile
           label={t("overview.subagents")}
+          help={t("common:insights.help.subagents")}
           value={stats.agents.subagent.toLocaleString()}
           hint={
             stats.agents.main > 0 ? t("overview.plusMain", { count: stats.agents.main }) : undefined
@@ -338,12 +349,14 @@ export function SessionOverview({ session, agents, stats: frozen }: SessionOverv
         />
         <StatTile
           label={t("overview.compactions")}
+          help={t("common:insights.help.compactions")}
           value={stats.agents.compaction.toLocaleString()}
           icon={<Layers className="w-3 h-3" />}
           tone="blue"
         />
         <StatTile
           label={t("overview.errors")}
+          help={t("common:insights.help.errors")}
           value={stats.error_count.toLocaleString()}
           icon={<AlertTriangle className="w-3 h-3" />}
           tone={stats.error_count > 0 ? "rose" : "default"}
@@ -478,7 +491,10 @@ export function SessionOverview({ session, agents, stats: frozen }: SessionOverv
       {totalTokens > 0 && (
         <div className="rounded-lg border border-surface-3 bg-surface-2/60 p-3.5">
           <div className="flex items-center justify-between mb-2.5">
-            <h3 className="text-xs font-semibold text-fg-secondary uppercase tracking-wider flex items-center gap-1.5">
+            <h3
+              className="text-xs font-semibold text-fg-secondary uppercase tracking-wider flex items-center gap-1.5 cursor-help"
+              title={t("common:insights.help.tokenFlow")}
+            >
               <Coins className="w-3.5 h-3.5 text-status-warning" />
               {t("overview.tokenFlow")}
             </h3>