feat(mentor): mentoring-specific Round Overview card grid (§B)

Renders above Round Details when round.roundType === 'MENTORING':
  - Top-line counts: requested + assigned (with awaiting badge)
  - Request window: countdown pill (amber <48h, red <12h)
  - Mentor pool: size + avg load + 'View all' link to /admin/mentors
  - Workspace activity: msgs / files / milestones / last activity

Round Details panel now shows 'Mentor Pool: N members' (linked) instead
of an always-empty 'Jury Group' row on MENTORING rounds.

Plan: docs/superpowers/plans/2026-04-28-pr5-mentor-round-overview.md

src/app/(admin)/admin/rounds/[roundId]/page.tsx

@@ -91,6 +91,7 @@ import { ProjectStatesTable } from '@/components/admin/round/project-states-tabl
 // SubmissionWindowManager removed — round dates + file requirements in Config are sufficient
 import { FileRequirementsEditor } from '@/components/admin/round/file-requirements-editor'
 import { FilteringDashboard } from '@/components/admin/round/filtering-dashboard'
+import { MentoringRoundOverview } from '@/components/admin/round/mentoring-round-overview'
 import { RankingDashboard } from '@/components/admin/round/ranking-dashboard'
 import { CoverageReport } from '@/components/admin/assignment/coverage-report'
 import { AssignmentPreviewSheet } from '@/components/admin/assignment/assignment-preview-sheet'
@@ -582,6 +583,14 @@ export default function RoundDetailPage() {
   const isFiltering = round?.roundType === 'FILTERING'
   const isEvaluation = round?.roundType === 'EVALUATION'
   const isMentoring = round?.roundType === 'MENTORING'
+
+  // Mentor pool size — used by Round Details panel below to replace the
+  // always-empty "Jury Group" row on MENTORING rounds.
+  const { data: mentorPool } = trpc.mentor.getMentorPool.useQuery(
+    {},
+    { enabled: isMentoring },
+  )
+  const mentorPoolSize = mentorPool?.poolSize ?? 0
   const hasJury = ['EVALUATION', 'LIVE_FINAL', 'DELIBERATION'].includes(round?.roundType ?? '')
   const hasAwards = roundAwards.length > 0
   const isSimpleAdvance = ['INTAKE', 'SUBMISSION', 'MENTORING'].includes(round?.roundType ?? '')
@@ -1469,6 +1478,9 @@ export default function RoundDetailPage() {
             />
           )}
 
+          {/* Mentoring-specific stats \u2014 only on MENTORING rounds */}
+          {isMentoring && <MentoringRoundOverview roundId={roundId} />}
+
           {/* Round Info + Project Breakdown */}
           <div className="grid gap-4 sm:grid-cols-2">
             <AnimatedCard index={2}>
@@ -1482,7 +1494,9 @@ export default function RoundDetailPage() {
                     { label: 'Status', value: <span className="font-medium">{statusCfg.label}</span> },
                     { label: 'Position', value: <span className="font-medium">{`Round ${(round.sortOrder ?? 0) + 1}${competition?.rounds ? ` of ${competition.rounds.length}` : ''}`}</span> },
                     ...(round.purposeKey ? [{ label: 'Purpose', value: <span className="font-medium">{round.purposeKey}</span> }] : []),
-                    { label: 'Jury Group', value: <span className="font-medium">{juryGroup ? juryGroup.name : '\u2014'}</span> },
+                    isMentoring
+                      ? { label: 'Mentor Pool', value: <Link href="/admin/mentors" className="font-medium hover:underline">{mentorPoolSize} member{mentorPoolSize === 1 ? '' : 's'}</Link> }
+                      : { label: 'Jury Group', value: <span className="font-medium">{juryGroup ? juryGroup.name : '\u2014'}</span> },
                     { label: 'Opens', value: <span className="font-medium">{round.windowOpenAt ? new Date(round.windowOpenAt).toLocaleString() : '\u2014'}</span> },
                     { label: 'Closes', value: <span className="font-medium">{round.windowCloseAt ? new Date(round.windowCloseAt).toLocaleString() : '\u2014'}</span> },
                   ].map((row, i) => (

src/components/admin/round/mentoring-round-overview.tsx

@@ -0,0 +1,217 @@
+'use client'
+
+import Link from 'next/link'
+import { trpc } from '@/lib/trpc/client'
+import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card'
+import { Badge } from '@/components/ui/badge'
+import { Skeleton } from '@/components/ui/skeleton'
+import {
+  ArrowRight,
+  Clock,
+  FileText,
+  MessageCircle,
+  Target,
+  UserCheck,
+  Users,
+} from 'lucide-react'
+
+interface Props {
+  roundId: string
+}
+
+function formatRelativeFuture(date: Date | null): { label: string; tone: 'normal' | 'amber' | 'red' } {
+  if (!date) return { label: '—', tone: 'normal' }
+  const ms = date.getTime() - Date.now()
+  if (ms <= 0) return { label: 'Closed', tone: 'red' }
+  const hours = Math.floor(ms / 3_600_000)
+  const days = Math.floor(hours / 24)
+  const tone: 'normal' | 'amber' | 'red' =
+    hours <= 12 ? 'red' : hours <= 48 ? 'amber' : 'normal'
+  const label = days > 0 ? `Closes in ${days}d` : `Closes in ${hours}h`
+  return { label, tone }
+}
+
+function formatRelativePast(date: Date | null): string {
+  if (!date) return '—'
+  const ms = Date.now() - date.getTime()
+  const minutes = Math.floor(ms / 60_000)
+  const hours = Math.floor(ms / 3_600_000)
+  const days = Math.floor(ms / 86_400_000)
+  if (days > 0) return `${days}d ago`
+  if (hours > 0) return `${hours}h ago`
+  return `${Math.max(0, minutes)}m ago`
+}
+
+export function MentoringRoundOverview({ roundId }: Props) {
+  const { data: stats, isLoading: statsLoading } = trpc.mentor.getRoundStats.useQuery(
+    { roundId },
+    { refetchInterval: 30_000 },
+  )
+  const { data: pool, isLoading: poolLoading } = trpc.mentor.getMentorPool.useQuery({})
+
+  if (statsLoading || poolLoading) {
+    return (
+      <div className="grid gap-4 md:grid-cols-2 xl:grid-cols-4">
+        {[1, 2, 3, 4].map((i) => (
+          <Skeleton key={i} className="h-32 w-full rounded-md" />
+        ))}
+      </div>
+    )
+  }
+  if (!stats || !pool) return null
+
+  const requestedPct = stats.totalProjects
+    ? Math.round((stats.requestedCount / stats.totalProjects) * 100)
+    : 0
+  const assignedPct = stats.totalProjects
+    ? Math.round((stats.assignedCount / stats.totalProjects) * 100)
+    : 0
+
+  const window = formatRelativeFuture(
+    stats.requestWindow.deadline ? new Date(stats.requestWindow.deadline) : null,
+  )
+
+  const avgLoad =
+    pool.poolSize > 0 ? (pool.totalCurrentAssignments / pool.poolSize).toFixed(1) : '—'
+  const lastActivity = stats.workspaceActivity.lastActivityAt
+    ? new Date(stats.workspaceActivity.lastActivityAt)
+    : null
+
+  return (
+    <div className="grid gap-4 md:grid-cols-2 xl:grid-cols-4">
+      <Card>
+        <CardHeader className="pb-2">
+          <CardTitle className="text-muted-foreground text-xs font-medium uppercase tracking-wide">
+            Requested mentoring
+          </CardTitle>
+        </CardHeader>
+        <CardContent>
+          <div className="text-3xl font-bold tabular-nums">
+            {stats.requestedCount}
+            <span className="text-muted-foreground ml-2 text-sm font-normal">
+              / {stats.totalProjects}
+            </span>
+          </div>
+          <p className="text-muted-foreground mt-1 text-xs">{requestedPct}% of round</p>
+        </CardContent>
+      </Card>
+
+      <Card>
+        <CardHeader className="pb-2">
+          <CardTitle className="text-muted-foreground text-xs font-medium uppercase tracking-wide">
+            Mentor assigned
+          </CardTitle>
+        </CardHeader>
+        <CardContent>
+          <div className="flex items-baseline gap-2">
+            <div className="text-3xl font-bold tabular-nums">{stats.assignedCount}</div>
+            <UserCheck className="text-muted-foreground h-5 w-5" />
+          </div>
+          <p className="text-muted-foreground mt-1 text-xs">
+            {assignedPct}% of round{' '}
+            {stats.awaitingAssignment > 0 && (
+              <span className="text-amber-700 dark:text-amber-400">
+                · {stats.awaitingAssignment} awaiting
+              </span>
+            )}
+          </p>
+        </CardContent>
+      </Card>
+
+      <Card>
+        <CardHeader className="pb-2">
+          <CardTitle className="text-muted-foreground text-xs font-medium uppercase tracking-wide">
+            Request window
+          </CardTitle>
+        </CardHeader>
+        <CardContent>
+          <div className="flex items-baseline gap-2">
+            <Clock className="text-muted-foreground h-5 w-5" />
+            <Badge
+              variant={
+                window.tone === 'red'
+                  ? 'destructive'
+                  : window.tone === 'amber'
+                    ? 'secondary'
+                    : 'outline'
+              }
+              className="text-sm"
+            >
+              {window.label}
+            </Badge>
+          </div>
+          <p className="text-muted-foreground mt-2 text-xs">
+            {stats.requestWindow.deadline
+              ? `Closes ${new Date(stats.requestWindow.deadline).toLocaleDateString()} · ${stats.requestWindow.deadlineDays}-day window`
+              : 'No window deadline set'}
+          </p>
+        </CardContent>
+      </Card>
+
+      <Card>
+        <CardHeader className="flex flex-row items-center justify-between pb-2">
+          <CardTitle className="text-muted-foreground text-xs font-medium uppercase tracking-wide">
+            Mentor pool
+          </CardTitle>
+          <Link
+            href="/admin/mentors"
+            className="text-muted-foreground hover:text-foreground inline-flex items-center text-xs"
+          >
+            View all
+            <ArrowRight className="ml-0.5 h-3 w-3" />
+          </Link>
+        </CardHeader>
+        <CardContent>
+          <div className="flex items-baseline gap-2">
+            <div className="text-3xl font-bold tabular-nums">{pool.poolSize}</div>
+            <Users className="text-muted-foreground h-5 w-5" />
+          </div>
+          <p className="text-muted-foreground mt-1 text-xs">
+            Avg load <span className="text-foreground font-medium">{avgLoad}</span> ·{' '}
+            {pool.totalCurrentAssignments} active
+          </p>
+        </CardContent>
+      </Card>
+
+      <Card className="md:col-span-2 xl:col-span-4">
+        <CardHeader className="pb-2">
+          <CardTitle className="text-sm">Workspace activity</CardTitle>
+        </CardHeader>
+        <CardContent>
+          <div className="grid grid-cols-2 gap-x-6 gap-y-3 text-sm md:grid-cols-4">
+            <div className="flex items-center gap-2">
+              <MessageCircle className="text-muted-foreground h-4 w-4" />
+              <div>
+                <div className="font-bold tabular-nums">{stats.workspaceActivity.messageCount}</div>
+                <div className="text-muted-foreground text-xs">messages</div>
+              </div>
+            </div>
+            <div className="flex items-center gap-2">
+              <FileText className="text-muted-foreground h-4 w-4" />
+              <div>
+                <div className="font-bold tabular-nums">{stats.workspaceActivity.fileCount}</div>
+                <div className="text-muted-foreground text-xs">files</div>
+              </div>
+            </div>
+            <div className="flex items-center gap-2">
+              <Target className="text-muted-foreground h-4 w-4" />
+              <div>
+                <div className="font-bold tabular-nums">
+                  {stats.workspaceActivity.milestoneCount}
+                </div>
+                <div className="text-muted-foreground text-xs">milestones</div>
+              </div>
+            </div>
+            <div className="flex items-center gap-2">
+              <Clock className="text-muted-foreground h-4 w-4" />
+              <div>
+                <div className="font-medium">{formatRelativePast(lastActivity)}</div>
+                <div className="text-muted-foreground text-xs">last activity</div>
+              </div>
+            </div>
+          </div>
+        </CardContent>
+      </Card>
+    </div>
+  )
+}