fix(P2-06): remove @Optional() silent skip from AiInteractive/Background workers

Engine is now a hard dependency — DI resolution failure prevents Worker
startup (fail-fast) instead of silently skipping all Unified Jobs.

Changes:
- ai-interactive.worker.ts: remove @Optional(), silent return guard
- ai-background.worker.ts: remove @Optional(), silent return guard
- docs: mark P2-06 as fixed

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

docs/architecture/m-ai-04-gate-audit.md

@@ -288,7 +288,7 @@ E2E 场景 12 验证通过。
 | P2-03 | FocusItem `knowledgeBaseId` 恒为 `unknown`（M-AI-04-01 #3） | 否 |
 | P2-04 | ModelRouter preferred/fallback 相同（M-AI-04-01 #7） | 否 |
 | P2-05 | ReviewCard 无 `jobId` 关联字段（表结构限制） | 否 |
-| **P2-06** | **`@Optional()` 静默吞任务** — `AiInteractiveJobWorker` 中 `if (!this.engine) return` 会在模块依赖再次出错时静默跳过 Unified Job，而非启动失败 | **生产 Unified 前移除** |
+| **P2-06** | **`@Optional()` 静默吞任务** — ✅ 已修复 (`4f74c09`)：`AiInteractiveJobWorker` + `AiBackgroundJobWorker` 移除 `@Optional()` 和 `if (!this.engine) return`。Engine 缺失时 DI 直接抛错阻止启动 | ✅ |
 | **P2-07** | **Engine 硬编码 `active_recall`** — 通用 Engine 中 4 处 `if (job.jobType === 'active_recall')` 分支，应重构为 Definition Hook 或 Observer 模式 | 否（不阻塞 M-AI-05） |
 
 ### P3

src/workers/ai-background.worker.ts

@@ -1,5 +1,5 @@
 import { Processor, WorkerHost } from '@nestjs/bullmq';
-import { Logger, Inject, Optional } from '@nestjs/common';
+import { Logger, Inject } from '@nestjs/common';
 import type { Job } from 'bullmq';
 import {
   QUEUE_AI_BACKGROUND,
@@ -25,11 +25,11 @@ export class AiBackgroundJobWorker extends WorkerHost {
   private readonly logger = new Logger(AiBackgroundJobWorker.name);
 
   constructor(
-    @Optional()
     @Inject(AI_JOB_EXECUTION_ENGINE)
-    private readonly engine?: any,
+    private readonly engine: any,
   ) {
     super();
+    // P2-06: Engine 是硬依赖。DI 解析失败 → Worker 启动 crash（fail-fast）。
   }
 
   async process(job: Job<{ jobId: string }>): Promise<void> {
@@ -40,15 +40,6 @@ export class AiBackgroundJobWorker extends WorkerHost {
       throw new Error('Invalid job payload: missing jobId');
     }
 
-    if (!this.engine) {
-      // M-AI-03-05~07 阶段 Engine 尚未实现，暂记日志并标记完成
-      this.logger.warn(
-        `Engine not available — skipping jobId=${jobId}. ` +
-        `Will be handled after M-AI-03-08 (#291).`,
-      );
-      return;
-    }
-
     const context = {
       jobId: job.id ?? '',
       attemptMade: job.attemptsMade,

src/workers/ai-interactive.worker.ts

@@ -1,5 +1,5 @@
 import { Processor, WorkerHost } from '@nestjs/bullmq';
-import { Logger, Inject, Optional } from '@nestjs/common';
+import { Logger, Inject } from '@nestjs/common';
 import type { Job } from 'bullmq';
 import {
   QUEUE_AI_INTERACTIVE,
@@ -25,11 +25,12 @@ export class AiInteractiveJobWorker extends WorkerHost {
   private readonly logger = new Logger(AiInteractiveJobWorker.name);
 
   constructor(
-    @Optional()
     @Inject(AI_JOB_EXECUTION_ENGINE)
-    private readonly engine?: any,
+    private readonly engine: any,
   ) {
     super();
+    // P2-06: Engine 是硬依赖。若 DI 解析失败，Worker 启动即 crash（fail-fast），
+    // 不复静默跳过 Unified Job。Kubernetes/systemd 负责重启。
   }
 
   async process(job: Job<{ jobId: string }>): Promise<void> {
@@ -40,15 +41,6 @@ export class AiInteractiveJobWorker extends WorkerHost {
       throw new Error('Invalid job payload: missing jobId');
     }
 
-    if (!this.engine) {
-      // M-AI-03-05~07 阶段 Engine 尚未实现，暂记日志并标记完成
-      this.logger.warn(
-        `Engine not available — skipping jobId=${jobId}. ` +
-        `Will be handled after M-AI-03-08 (#291).`,
-      );
-      return;
-    }
-
     const context = {
       jobId: job.id ?? '',
       attemptMade: job.attemptsMade,