test(mentor): cover multi-mentor stacking + change-request procedures (PR8 Task 10)

- multi-mentor-assignment.test.ts: stacking, P2002 dup-pair, per-team email
  idempotency via notificationSentAt, requestChange/list/resolve auth +
  conflict semantics
- mentor-file-scope.test.ts: schema invariant (projectId required, dropping
  the originating assignment leaves the file in place via SetNull)

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

tests/integration/mentor-file-scope.test.ts

@@ -0,0 +1,138 @@
+/**
+ * PR8 — MentorFile schema invariant check
+ *
+ * The actual data migration (backfill of MentorFile.projectId from the
+ * originating MentorAssignment.projectId) was verified against the May 7
+ * production database dump in Task 2 of PR8. This file is a complementary
+ * schema-invariant check that runs against the current dev DB:
+ *
+ *   1. MentorFile.projectId is now a required column (Prisma validation fails
+ *      when omitted).
+ *   2. Files are scoped to the project, not to a single MentorAssignment —
+ *      deleting the originating assignment leaves the file in place with
+ *      mentorAssignmentId set to NULL (FK SetNull) and projectId unchanged.
+ *      This is what enables team-wide file visibility across co-mentors.
+ */
+
+import { afterAll, describe, expect, it } from 'vitest'
+import { prisma } from '../setup'
+import {
+  createTestUser,
+  createTestProgram,
+  createTestProject,
+  cleanupTestData,
+  uid,
+} from '../helpers'
+
+describe('MentorFile scope invariants (PR8 schema)', () => {
+  const programIds: string[] = []
+  const userIds: string[] = []
+  const mentorFileIds: string[] = []
+
+  afterAll(async () => {
+    if (mentorFileIds.length > 0) {
+      await prisma.mentorFile.deleteMany({ where: { id: { in: mentorFileIds } } })
+    }
+    for (const programId of programIds) {
+      await prisma.mentorAssignment.deleteMany({ where: { project: { programId } } })
+      await prisma.mentorFile.deleteMany({ where: { project: { programId } } })
+      await cleanupTestData(programId, [])
+    }
+    if (userIds.length > 0) {
+      await prisma.user.deleteMany({ where: { id: { in: userIds } } })
+    }
+  })
+
+  it('MentorFile.projectId matches MentorAssignment.projectId when created via the workspace path', async () => {
+    const program = await createTestProgram({ name: `mfscope-match-${uid()}` })
+    programIds.push(program.id)
+    const project = await createTestProject(program.id, { title: 'Scope Match' })
+    const mentor = await createTestUser('MENTOR')
+    userIds.push(mentor.id)
+
+    const assignment = await prisma.mentorAssignment.create({
+      data: {
+        projectId: project.id,
+        mentorId: mentor.id,
+        method: 'MANUAL',
+        workspaceEnabled: true,
+      },
+    })
+
+    const file = await prisma.mentorFile.create({
+      data: {
+        projectId: project.id,
+        mentorAssignmentId: assignment.id,
+        uploadedByUserId: mentor.id,
+        fileName: 'invariant.pdf',
+        mimeType: 'application/pdf',
+        size: 1024,
+        bucket: 'mopc-files',
+        objectKey: `Scope_Match/mentorship/${Date.now()}-invariant.pdf`,
+      },
+    })
+    mentorFileIds.push(file.id)
+
+    expect(file.projectId).toBe(assignment.projectId)
+  })
+
+  it('creating a MentorFile without a projectId is rejected by Prisma', async () => {
+    const program = await createTestProgram({ name: `mfscope-noproj-${uid()}` })
+    programIds.push(program.id)
+    const mentor = await createTestUser('MENTOR')
+    userIds.push(mentor.id)
+
+    // `projectId` is required in the schema — Prisma should reject this.
+    // Cast away the type for the deliberate omission.
+    await expect(
+      prisma.mentorFile.create({
+        data: {
+          uploadedByUserId: mentor.id,
+          fileName: 'no-project.pdf',
+          mimeType: 'application/pdf',
+          size: 10,
+          bucket: 'mopc-files',
+          objectKey: 'orphan/no-project.pdf',
+        } as unknown as Parameters<typeof prisma.mentorFile.create>[0]['data'],
+      }),
+    ).rejects.toThrow()
+  })
+
+  it('dropping the originating MentorAssignment leaves the MentorFile in place (SetNull)', async () => {
+    const program = await createTestProgram({ name: `mfscope-setnull-${uid()}` })
+    programIds.push(program.id)
+    const project = await createTestProject(program.id, { title: 'SetNull Project' })
+    const mentor = await createTestUser('MENTOR')
+    userIds.push(mentor.id)
+
+    const assignment = await prisma.mentorAssignment.create({
+      data: {
+        projectId: project.id,
+        mentorId: mentor.id,
+        method: 'MANUAL',
+        workspaceEnabled: true,
+      },
+    })
+
+    const file = await prisma.mentorFile.create({
+      data: {
+        projectId: project.id,
+        mentorAssignmentId: assignment.id,
+        uploadedByUserId: mentor.id,
+        fileName: 'survives-drop.pdf',
+        mimeType: 'application/pdf',
+        size: 2048,
+        bucket: 'mopc-files',
+        objectKey: `SetNull_Project/mentorship/${Date.now()}-survives.pdf`,
+      },
+    })
+    mentorFileIds.push(file.id)
+
+    await prisma.mentorAssignment.delete({ where: { id: assignment.id } })
+
+    const after = await prisma.mentorFile.findUnique({ where: { id: file.id } })
+    expect(after).not.toBeNull()
+    expect(after?.mentorAssignmentId).toBeNull()
+    expect(after?.projectId).toBe(project.id)
+  })
+})