feat(#166): Implement Stitcher module structure

Created the mosaic-stitcher module - the workflow orchestration layer
that wraps OpenClaw.

Responsibilities:
- Receive webhooks from @mosaic bot
- Apply Guard Rails (capability permissions)
- Apply Quality Rails (mandatory gates)
- Track all job steps and events
- Dispatch work to OpenClaw with constraints

Implementation:
- StitcherModule: Module definition with PrismaModule and BullMqModule
- StitcherService: Core orchestration logic
  - handleWebhook(): Process webhooks from @mosaic bot
  - dispatchJob(): Create RunnerJob and dispatch to BullMQ queue
  - applyGuardRails(): Check capability permissions for agent profiles
  - applyQualityRails(): Determine mandatory gates for job types
  - trackJobEvent(): Log events to database for audit trail
- StitcherController: HTTP endpoints
  - POST /stitcher/webhook: Webhook receiver
  - POST /stitcher/dispatch: Manual job dispatch
- DTOs and interfaces for type safety

TDD Process:
1. RED: Created failing tests (12 tests)
2. GREEN: Implemented minimal code to pass tests
3. REFACTOR: Fixed TypeScript strict mode issues

Quality Gates: ALL PASS
- Typecheck: PASS
- Lint: PASS
- Build: PASS
- Tests: PASS (12/12)

Token estimate: ~56,000 tokens

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

apps/api/src/stitcher/stitcher.controller.ts

@@ -0,0 +1,37 @@
+import { Controller, Post, Body } from "@nestjs/common";
+import { StitcherService } from "./stitcher.service";
+import { WebhookPayloadDto, DispatchJobDto } from "./dto";
+import type { JobDispatchResult, JobDispatchContext } from "./interfaces";
+
+/**
+ * StitcherController - Webhook and job dispatch endpoints
+ *
+ * Handles incoming webhooks from @mosaic bot and provides
+ * endpoints for manual job dispatch
+ */
+@Controller("stitcher")
+export class StitcherController {
+  constructor(private readonly stitcherService: StitcherService) {}
+
+  /**
+   * Webhook endpoint for @mosaic bot
+   */
+  @Post("webhook")
+  async webhook(@Body() payload: WebhookPayloadDto): Promise<JobDispatchResult> {
+    return this.stitcherService.handleWebhook(payload);
+  }
+
+  /**
+   * Manual job dispatch endpoint
+   */
+  @Post("dispatch")
+  async dispatch(@Body() dto: DispatchJobDto): Promise<JobDispatchResult> {
+    const context: JobDispatchContext = {
+      workspaceId: dto.workspaceId,
+      type: dto.type,
+      ...(dto.context !== undefined && { metadata: dto.context }),
+    };
+
+    return this.stitcherService.dispatchJob(context);
+  }
+}