feat(documents): folder service · rename + move + soft-rescue delete

renameFolder + moveFolder enforce sibling-name uniqueness via the
shared isSiblingNameConflict helper and reject cross-port leakage at
the service boundary. moveFolder walks the destination's ancestor
chain to refuse cycles before the write.

deleteFolderSoftRescue re-parents every child folder and document up
to the deleted folder's parent (or to root) inside a transaction,
then drops the folder row. Children never disappear silently — a
wrong click moves work up the tree, never deletes it. Audit-logged
with rescuedTo metadata.

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

tests/integration/document-folders-crud.test.ts

@@ -1,5 +1,6 @@
 /**
  * Task 3 — document-folders service: listTree + createFolder (TDD).
+ * Task 4 — renameFolder + moveFolder (TDD).
  *
  * Uses the makePort factory (not a "setupTestPort" helper — that name
  * doesn't exist in this codebase). TEST_USER_ID is resolved once via
@@ -14,7 +15,12 @@ import { eq } from 'drizzle-orm';
 import { db } from '@/lib/db';
 import { documentFolders } from '@/lib/db/schema/documents';
 import { user } from '@/lib/db/schema/users';
-import { listTree, createFolder } from '@/lib/services/document-folders.service';
+import {
+  listTree,
+  createFolder,
+  renameFolder,
+  moveFolder,
+} from '@/lib/services/document-folders.service';
 import { makePort } from '../helpers/factories';
 
 let TEST_USER_ID = '';
@@ -96,3 +102,71 @@ describe('document-folders service · createFolder unique-sibling guard', () =>
     ).rejects.toThrow(/invalid parent/i);
   });
 });
+
+describe('document-folders service · renameFolder', () => {
+  let portId: string;
+
+  beforeEach(async () => {
+    const port = await makePort();
+    portId = port.id;
+    await db.delete(documentFolders).where(eq(documentFolders.portId, portId));
+  });
+
+  it('renames a folder and bumps updatedAt', async () => {
+    const folder = await createFolder(portId, TEST_USER_ID, { name: 'Old', parentId: null });
+    const before = folder.updatedAt.getTime();
+    await new Promise((r) => setTimeout(r, 10));
+    const renamed = await renameFolder(portId, folder.id, 'New');
+    expect(renamed.name).toBe('New');
+    expect(renamed.updatedAt.getTime()).toBeGreaterThan(before);
+  });
+
+  it('rejects rename to an existing sibling name', async () => {
+    await createFolder(portId, TEST_USER_ID, { name: 'Existing', parentId: null });
+    const folder = await createFolder(portId, TEST_USER_ID, { name: 'Mine', parentId: null });
+    await expect(renameFolder(portId, folder.id, 'Existing')).rejects.toThrow(/already exists/i);
+  });
+
+  it('throws NotFound when the folder belongs to another port', async () => {
+    const otherPort = await makePort();
+    const folder = await createFolder(otherPort.id, TEST_USER_ID, { name: 'X', parentId: null });
+    await expect(renameFolder(portId, folder.id, 'Y')).rejects.toThrow(/couldn't find/i);
+  });
+});
+
+describe('document-folders service · moveFolder', () => {
+  let portId: string;
+
+  beforeEach(async () => {
+    const port = await makePort();
+    portId = port.id;
+    await db.delete(documentFolders).where(eq(documentFolders.portId, portId));
+  });
+
+  it('moves a folder under a new parent', async () => {
+    const root = await createFolder(portId, TEST_USER_ID, { name: 'Root', parentId: null });
+    const orphan = await createFolder(portId, TEST_USER_ID, { name: 'Orphan', parentId: null });
+    const moved = await moveFolder(portId, orphan.id, root.id);
+    expect(moved.parentId).toBe(root.id);
+  });
+
+  it('moves a folder back to root with parentId=null', async () => {
+    const root = await createFolder(portId, TEST_USER_ID, { name: 'Root', parentId: null });
+    const child = await createFolder(portId, TEST_USER_ID, { name: 'Child', parentId: root.id });
+    const moved = await moveFolder(portId, child.id, null);
+    expect(moved.parentId).toBeNull();
+  });
+
+  it('rejects a move that would create a cycle', async () => {
+    const a = await createFolder(portId, TEST_USER_ID, { name: 'A', parentId: null });
+    const b = await createFolder(portId, TEST_USER_ID, { name: 'B', parentId: a.id });
+    const c = await createFolder(portId, TEST_USER_ID, { name: 'C', parentId: b.id });
+    // moving A under C would create A → B → C → A
+    await expect(moveFolder(portId, a.id, c.id)).rejects.toThrow(/cycle/i);
+  });
+
+  it('rejects moving a folder under itself', async () => {
+    const a = await createFolder(portId, TEST_USER_ID, { name: 'A', parentId: null });
+    await expect(moveFolder(portId, a.id, a.id)).rejects.toThrow(/cycle/i);
+  });
+});