feat: Add errands schema, repository, and wire into tRPC context/container

Creates the errands table (with conflictFiles column), errand-repository
port interface, DrizzleErrandRepository adapter, and wires the repository
into TRPCContext, the DI container, _helpers.ts requireErrandRepository guard,
and the test harness. Also fixes pre-existing TS error in controller.test.ts.

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

apps/server/trpc/routers/_helpers.ts

@@ -19,6 +19,7 @@ import type { LogChunkRepository } from '../../db/repositories/log-chunk-reposit
 import type { ConversationRepository } from '../../db/repositories/conversation-repository.js';
 import type { ChatSessionRepository } from '../../db/repositories/chat-session-repository.js';
 import type { ReviewCommentRepository } from '../../db/repositories/review-comment-repository.js';
+import type { ErrandRepository } from '../../db/repositories/errand-repository.js';
 import type { DispatchManager, PhaseDispatchManager } from '../../dispatch/types.js';
 import type { CoordinationManager } from '../../coordination/types.js';
 import type { BranchManager } from '../../git/branch-manager.js';
@@ -225,3 +226,13 @@ export function requireProjectSyncManager(ctx: TRPCContext): ProjectSyncManager
   }
   return ctx.projectSyncManager;
 }
+
+export function requireErrandRepository(ctx: TRPCContext): ErrandRepository {
+  if (!ctx.errandRepository) {
+    throw new TRPCError({
+      code: 'INTERNAL_SERVER_ERROR',
+      message: 'Errand repository not available',
+    });
+  }
+  return ctx.errandRepository;
+}