feat: mentor self-drop with required reason

Adds mentor.dropAssignment mutation (mentor-only, ownership-checked, reason
min 10 chars). Filters dropped MentorAssignment rows out of getMyProjects,
getCandidates mentor count, getMentorPool, and getMenteeActivity so they
no longer surface in the mentor or admin UI.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

tests/unit/mentor-drop.test.ts

@@ -0,0 +1,201 @@
+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'
+
+async function createMentor() {
+  const id = uid('user')
+  return prisma.user.create({
+    data: {
+      id,
+      email: `${id}@test.local`,
+      name: 'Test Mentor',
+      role: 'MENTOR',
+      roles: ['MENTOR'],
+      status: 'ACTIVE',
+    },
+  })
+}
+
+describe('mentor.dropAssignment', () => {
+  const programIds: string[] = []
+  const userIds: string[] = []
+
+  afterAll(async () => {
+    for (const programId of programIds) {
+      await prisma.mentorAssignment.deleteMany({ where: { project: { programId } } })
+      await cleanupTestData(programId, [])
+    }
+    if (userIds.length > 0) {
+      await prisma.user.deleteMany({ where: { id: { in: userIds } } })
+    }
+  })
+
+  it('mentor can drop their own assignment with a valid reason', async () => {
+    const mentor = await createMentor()
+    userIds.push(mentor.id)
+    const admin = await createTestUser('SUPER_ADMIN')
+    userIds.push(admin.id)
+    const program = await createTestProgram({ name: `drop-ok-${uid()}` })
+    programIds.push(program.id)
+    const project = await createTestProject(program.id, { title: 'P', competitionCategory: 'STARTUP' })
+    const ma = await prisma.mentorAssignment.create({
+      data: {
+        projectId: project.id,
+        mentorId: mentor.id,
+        method: 'MANUAL',
+        assignedBy: admin.id,
+        workspaceEnabled: true,
+      },
+    })
+
+    const caller = createCaller(mentorRouter, {
+      id: mentor.id,
+      email: mentor.email,
+      role: 'MENTOR',
+    })
+    const result = await caller.dropAssignment({
+      assignmentId: ma.id,
+      reason: 'Schedule conflict — cannot dedicate enough time',
+    })
+    expect(result.droppedAt).not.toBeNull()
+    expect(result.droppedBy).toBe('mentor')
+    expect(result.droppedReason).toContain('Schedule conflict')
+  })
+
+  it('rejects when reason is too short', async () => {
+    const mentor = await createMentor()
+    userIds.push(mentor.id)
+    const admin = await createTestUser('SUPER_ADMIN')
+    userIds.push(admin.id)
+    const program = await createTestProgram({ name: `drop-short-${uid()}` })
+    programIds.push(program.id)
+    const project = await createTestProject(program.id, {
+      title: 'P',
+      competitionCategory: 'STARTUP',
+    })
+    const ma = await prisma.mentorAssignment.create({
+      data: {
+        projectId: project.id,
+        mentorId: mentor.id,
+        method: 'MANUAL',
+        assignedBy: admin.id,
+      },
+    })
+    const caller = createCaller(mentorRouter, {
+      id: mentor.id,
+      email: mentor.email,
+      role: 'MENTOR',
+    })
+    await expect(
+      caller.dropAssignment({ assignmentId: ma.id, reason: 'short' }),
+    ).rejects.toThrow()
+  })
+
+  it('rejects when mentor does not own the assignment', async () => {
+    const mentorA = await createMentor()
+    const mentorB = await createMentor()
+    userIds.push(mentorA.id, mentorB.id)
+    const admin = await createTestUser('SUPER_ADMIN')
+    userIds.push(admin.id)
+    const program = await createTestProgram({ name: `drop-foreign-${uid()}` })
+    programIds.push(program.id)
+    const project = await createTestProject(program.id, {
+      title: 'P',
+      competitionCategory: 'STARTUP',
+    })
+    const ma = await prisma.mentorAssignment.create({
+      data: {
+        projectId: project.id,
+        mentorId: mentorA.id,
+        method: 'MANUAL',
+        assignedBy: admin.id,
+      },
+    })
+    const callerB = createCaller(mentorRouter, {
+      id: mentorB.id,
+      email: mentorB.email,
+      role: 'MENTOR',
+    })
+    await expect(
+      callerB.dropAssignment({
+        assignmentId: ma.id,
+        reason: 'Trying to steal the drop',
+      }),
+    ).rejects.toThrow(/not your assignment/i)
+  })
+
+  it('rejects already-dropped assignments', async () => {
+    const mentor = await createMentor()
+    userIds.push(mentor.id)
+    const admin = await createTestUser('SUPER_ADMIN')
+    userIds.push(admin.id)
+    const program = await createTestProgram({ name: `drop-twice-${uid()}` })
+    programIds.push(program.id)
+    const project = await createTestProject(program.id, {
+      title: 'P',
+      competitionCategory: 'STARTUP',
+    })
+    const ma = await prisma.mentorAssignment.create({
+      data: {
+        projectId: project.id,
+        mentorId: mentor.id,
+        method: 'MANUAL',
+        assignedBy: admin.id,
+        droppedAt: new Date(),
+        droppedReason: 'already dropped',
+        droppedBy: 'mentor',
+      },
+    })
+    const caller = createCaller(mentorRouter, {
+      id: mentor.id,
+      email: mentor.email,
+      role: 'MENTOR',
+    })
+    await expect(
+      caller.dropAssignment({
+        assignmentId: ma.id,
+        reason: 'Trying to drop again',
+      }),
+    ).rejects.toThrow(/already dropped/i)
+  })
+
+  it('rejects already-completed assignments', async () => {
+    const mentor = await createMentor()
+    userIds.push(mentor.id)
+    const admin = await createTestUser('SUPER_ADMIN')
+    userIds.push(admin.id)
+    const program = await createTestProgram({ name: `drop-completed-${uid()}` })
+    programIds.push(program.id)
+    const project = await createTestProject(program.id, {
+      title: 'P',
+      competitionCategory: 'STARTUP',
+    })
+    const ma = await prisma.mentorAssignment.create({
+      data: {
+        projectId: project.id,
+        mentorId: mentor.id,
+        method: 'MANUAL',
+        assignedBy: admin.id,
+        completionStatus: 'completed',
+      },
+    })
+    const caller = createCaller(mentorRouter, {
+      id: mentor.id,
+      email: mentor.email,
+      role: 'MENTOR',
+    })
+    await expect(
+      caller.dropAssignment({
+        assignmentId: ma.id,
+        reason: 'Already wrapped up the project',
+      }),
+    ).rejects.toThrow(/already completed/i)
+  })
+})