feat: 实现AI拒答机制和语言控制优化

- 添加 RunStatus.REFUSED 状态，AI可明确表达拒答意图
- 优化 System Prompt 使用视觉强调提高AI对拒答规则的遵守
- User Prompt 添加 SCOPE CHECK 和语言约束
- Worker Rules 添加多语言版本角色扮演规则
- Runner 传递 language 参数到 worker stage
- json_finalize 添加语言约束参数
- 更新单元测试匹配新的 prompt 结构

.trellis/tasks/04-28-fix-ai-english-output/task.json

@@ -0,0 +1,44 @@
+{
+  "id": "fix-ai-english-output",
+  "name": "fix-ai-english-output",
+  "title": "Fix AI English Output - Worker Role Playing Ignores Language Parameter",
+  "description": "Worker role-playing prompt always returns Chinese regardless of language parameter, causing AI to output Chinese even when user selects English.",
+  "status": "planning",
+  "dev_type": null,
+  "scope": null,
+  "priority": "P0",
+  "creator": "zl-q",
+  "assignee": "zl-q",
+  "createdAt": "2026-04-28",
+  "completedAt": null,
+  "branch": null,
+  "base_branch": "dev",
+  "worktree_path": null,
+  "current_phase": 0,
+  "next_action": [
+    {
+      "phase": 1,
+      "action": "implement"
+    },
+    {
+      "phase": 2,
+      "action": "check"
+    },
+    {
+      "phase": 3,
+      "action": "finish"
+    },
+    {
+      "phase": 4,
+      "action": "create-pr"
+    }
+  ],
+  "commit": null,
+  "pr_url": null,
+  "subtasks": [],
+  "children": [],
+  "parent": null,
+  "relatedFiles": [],
+  "notes": "",
+  "meta": {}
+}