feat: Mentees & Activity tab on /admin/mentors

Adds a project-centric ops view for mentor management:
- New mentor.getMenteeActivity tRPC procedure aggregates every project
  with wantsMentorship=true and derives a status (unassigned / assigned
  / active / stalled) from the latest message + file activity.
- /admin/mentors becomes a tabbed page: existing Mentor list +
  new Mentees & Activity table with status pills, search, and a
  per-row Assign/Open CTA linking to /admin/projects/[id]/mentor.
- Includes 2 unit tests covering classification + program scoping.

Also: ignore .remember/ (plugin scratch dir).

tests/unit/mentee-activity.test.ts

@@ -0,0 +1,167 @@
+import { afterAll, describe, expect, it } from 'vitest'
+import { prisma, createCaller } from '../setup'
+import {
+  createTestUser,
+  createTestProgram,
+  createTestProject,
+  cleanupTestData,
+  uid,
+} from '../helpers'
+import { mentorRouter } from '../../src/server/routers/mentor'
+import type { UserRole } from '@prisma/client'
+
+async function createUserWithRoles(primaryRole: UserRole, rolesArray: UserRole[]) {
+  const id = uid('user')
+  return prisma.user.create({
+    data: {
+      id,
+      email: `${id}@test.local`,
+      name: `Test ${primaryRole}`,
+      role: primaryRole,
+      roles: rolesArray,
+      status: 'ACTIVE',
+    },
+  })
+}
+
+const DAY = 86_400_000
+
+describe('mentor.getMenteeActivity', () => {
+  const programIds: string[] = []
+  const userIds: string[] = []
+
+  afterAll(async () => {
+    for (const programId of programIds) {
+      await prisma.mentorAssignment.deleteMany({ where: { project: { programId } } })
+      await cleanupTestData(programId, [])
+    }
+    if (userIds.length > 0) {
+      await prisma.user.deleteMany({ where: { id: { in: userIds } } })
+    }
+  })
+
+  it('classifies projects as unassigned / assigned / active / stalled and returns totals', async () => {
+    const admin = await createTestUser('SUPER_ADMIN')
+    userIds.push(admin.id)
+    const program = await createTestProgram({ name: `mentee-activity-${uid()}` })
+    programIds.push(program.id)
+
+    const lead = await createUserWithRoles('APPLICANT', ['APPLICANT'])
+    userIds.push(lead.id)
+    const mentor = await createUserWithRoles('MENTOR', ['MENTOR'])
+    userIds.push(mentor.id)
+
+    // Four projects all wantsMentorship
+    const pUnassigned = await createTestProject(program.id, { title: 'Unassigned' })
+    const pAssigned = await createTestProject(program.id, { title: 'Assigned' })
+    const pActive = await createTestProject(program.id, { title: 'Active' })
+    const pStalled = await createTestProject(program.id, { title: 'Stalled' })
+    for (const p of [pUnassigned, pAssigned, pActive, pStalled]) {
+      await prisma.project.update({ where: { id: p.id }, data: { wantsMentorship: true } })
+      await prisma.teamMember.create({
+        data: { projectId: p.id, userId: lead.id, role: 'LEAD' },
+      })
+    }
+
+    // Assigned: mentor assigned, no activity yet
+    await prisma.mentorAssignment.create({
+      data: {
+        projectId: pAssigned.id,
+        mentorId: mentor.id,
+        method: 'MANUAL',
+        assignedBy: admin.id,
+        workspaceEnabled: true,
+      },
+    })
+
+    // Active: mentor + recent message
+    const aActive = await prisma.mentorAssignment.create({
+      data: {
+        projectId: pActive.id,
+        mentorId: mentor.id,
+        method: 'MANUAL',
+        assignedBy: admin.id,
+        workspaceEnabled: true,
+      },
+    })
+    await prisma.mentorMessage.create({
+      data: {
+        projectId: pActive.id,
+        senderId: mentor.id,
+        message: 'recent ping',
+        workspaceId: aActive.id,
+        createdAt: new Date(Date.now() - 2 * DAY),
+      },
+    })
+
+    // Stalled: mentor + last message > 14 days ago
+    const aStalled = await prisma.mentorAssignment.create({
+      data: {
+        projectId: pStalled.id,
+        mentorId: mentor.id,
+        method: 'MANUAL',
+        assignedBy: admin.id,
+        workspaceEnabled: true,
+        assignedAt: new Date(Date.now() - 30 * DAY),
+      },
+    })
+    await prisma.mentorMessage.create({
+      data: {
+        projectId: pStalled.id,
+        senderId: mentor.id,
+        message: 'old ping',
+        workspaceId: aStalled.id,
+        createdAt: new Date(Date.now() - 20 * DAY),
+      },
+    })
+
+    const caller = createCaller(mentorRouter, {
+      id: admin.id,
+      email: admin.email,
+      role: 'SUPER_ADMIN',
+    })
+    const result = await caller.getMenteeActivity({ programId: program.id })
+
+    const byTitle = Object.fromEntries(
+      result.rows.map((r: (typeof result.rows)[number]) => [r.project.title, r]),
+    )
+    expect(byTitle['Unassigned'].status).toBe('unassigned')
+    expect(byTitle['Unassigned'].mentor).toBeNull()
+    expect(byTitle['Assigned'].status).toBe('assigned')
+    expect(byTitle['Assigned'].mentor?.id).toBe(mentor.id)
+    expect(byTitle['Active'].status).toBe('active')
+    expect(byTitle['Active'].lastActivityAt).not.toBeNull()
+    expect(byTitle['Stalled'].status).toBe('stalled')
+
+    expect(result.totals.unassigned).toBe(1)
+    expect(result.totals.assigned).toBe(1)
+    expect(result.totals.active).toBe(1)
+    expect(result.totals.stalled).toBe(1)
+
+    // Team lead resolved
+    expect(byTitle['Active'].teamLead?.email).toBe(lead.email)
+  })
+
+  it('only includes projects that wantMentorship within the program scope', async () => {
+    const admin = await createTestUser('SUPER_ADMIN')
+    userIds.push(admin.id)
+    const program = await createTestProgram({ name: `mentee-scope-${uid()}` })
+    programIds.push(program.id)
+
+    const pYes = await createTestProject(program.id, { title: 'Yes' })
+    const pNo = await createTestProject(program.id, { title: 'No' })
+    await prisma.project.update({ where: { id: pYes.id }, data: { wantsMentorship: true } })
+    await prisma.project.update({ where: { id: pNo.id }, data: { wantsMentorship: false } })
+
+    const caller = createCaller(mentorRouter, {
+      id: admin.id,
+      email: admin.email,
+      role: 'SUPER_ADMIN',
+    })
+    const result = await caller.getMenteeActivity({ programId: program.id })
+
+    expect(
+      result.rows.map((r: (typeof result.rows)[number]) => r.project.title).sort(),
+    ).toEqual(['Yes'])
+  })
+})