feat: wire conflictFiles through errand.get and add repository tests

- `errand.get` now returns `conflictFiles: string[]` (always an array,
  never null) with defensive JSON.parse error handling
- `errand.get` returns `projectPath: string | null` computed from
  workspaceRoot + getProjectCloneDir so cw errand resolve can locate
  the worktree without a second tRPC call
- Add `apps/server/db/repositories/drizzle/errand.test.ts` covering
  conflictFiles store/retrieve, null for non-conflict errands, and
  findAll including conflictFiles
- Update `errand.test.ts` mock to include getProjectCloneDir and fix
  conflictFiles expectation from null to []

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/server/trpc/routers/errand.test.ts

@@ -35,6 +35,7 @@ vi.mock('../../git/manager.js', () => ({
 
 vi.mock('../../git/project-clones.js', () => ({
   ensureProjectClone: mockEnsureProjectClone,
+  getProjectCloneDir: vi.fn().mockReturnValue('repos/test-project-abc123'),
 }));
 
 vi.mock('../../agent/file-io.js', async (importOriginal) => {
@@ -393,7 +394,7 @@ describe('errand procedures', () => {
 
       expect(result.id).toBe(errand.id);
       expect(result).toHaveProperty('agentAlias');
-      expect(result.conflictFiles).toBeNull();
+      expect(result.conflictFiles).toEqual([]);
     });
 
     it('parses conflictFiles JSON when present', async () => {

apps/server/trpc/routers/errand.ts

@@ -18,8 +18,9 @@ import {
 } from './_helpers.js';
 import { writeErrandManifest } from '../../agent/file-io.js';
 import { buildErrandPrompt } from '../../agent/prompts/index.js';
+import { join } from 'node:path';
 import { SimpleGitWorktreeManager } from '../../git/manager.js';
-import { ensureProjectClone } from '../../git/project-clones.js';
+import { ensureProjectClone, getProjectCloneDir } from '../../git/project-clones.js';
 import type { TRPCContext } from '../context.js';
 
 // ErrandStatus values for input validation
@@ -200,10 +201,27 @@ export function errandProcedures(publicProcedure: ProcedureBuilder) {
           if (!errand) {
             throw new TRPCError({ code: 'NOT_FOUND', message: 'Errand not found' });
           }
-          return {
-            ...errand,
-            conflictFiles: errand.conflictFiles ? (JSON.parse(errand.conflictFiles) as string[]) : null,
-          };
+
+          // Parse conflictFiles; return [] on null or malformed JSON
+          let conflictFiles: string[] = [];
+          if (errand.conflictFiles) {
+            try {
+              conflictFiles = JSON.parse(errand.conflictFiles) as string[];
+            } catch {
+              conflictFiles = [];
+            }
+          }
+
+          // Compute project clone path for cw errand resolve
+          let projectPath: string | null = null;
+          if (errand.projectId && ctx.workspaceRoot) {
+            const project = await requireProjectRepository(ctx).findById(errand.projectId);
+            if (project) {
+              projectPath = join(ctx.workspaceRoot, getProjectCloneDir(project.name, project.id));
+            }
+          }
+
+          return { ...errand, conflictFiles, projectPath };
         }),
 
       // -----------------------------------------------------------------------