[moz] fix(§21): GAP-1 issue_assigned 6路分流 + GAP-2 issue_closed auto-pass + GAP-3 Discussion Prompt v3

第一轮背靠背一致性检查发现的 3 个 GAP：

GAP-1: §21 §5 issue_assigned 按 type label 分流
- 从 labels 解析 business_type (feature/impl/bug/docs/refactor/test)
- 从 toolchain-templates.yaml get_steps() 获取对应 steps
- fallback 到硬编码 steps（向后兼容）

GAP-2: §21 §11 Issue closed 事件处理
- toolchain_handler verify 加 issue_closed auto-pass
- toolchain_routes 加 issue closed webhook → 纯通知 task

GAP-3: §21 §13.2 Discussion Prompt v3
- 新增 你是谁 段（agent_identity 注入）
- 新增 你必须做什么 4 维度（定位/建议/认领/风险）
- 新增 Comment 格式（角色名开头）
- Boids 行为准则不变
- 黑板 API 不变（§21 范围仅 toolchain）

src/api/toolchain_routes.py

@@ -1025,14 +1025,36 @@ async def _handle_issues(payload: Dict[str, Any]) -> None:
                 },
             )
         else:
-            title = f"Issue 指派: {issue_title} ({repo}#{issue_number})"
-            _send_toolchain_task(
-                to_agent=assignee,
-                title=title,
-                description=text,
-                event_type="issue_assigned",
-                action_type="issue_assigned",
-                steps=[
+            # §21 §5 按 type/* label 解析 business_type
+            business_type = "feature"  # default
+            for lbl in labels_list:
+                lbl_lower = lbl.lower()
+                if "bug" in lbl_lower:
+                    business_type = "bug"
+                elif "impl" in lbl_lower or "feature" in lbl_lower:
+                    business_type = "feature" if "feature" in lbl_lower else "impl"
+                elif "docs" in lbl_lower or "documentation" in lbl_lower:
+                    business_type = "docs"
+                elif "refactor" in lbl_lower:
+                    business_type = "refactor"
+                elif "test" in lbl_lower:
+                    business_type = "test"
+
+            # §21 §4 从 YAML 模板获取 steps（fallback 到硬编码）
+            from src.daemon.toolchain_templates import get_steps
+            yaml_steps = get_steps("issue_assigned", business_type)
+            if yaml_steps:
+                # 渲染占位符
+                rendered_steps = []
+                for s in yaml_steps:
+                    s = s.replace("{issue_number}", str(issue_number))
+                    s = s.replace("{brief}", brief)
+                    s = s.replace("{title}", issue_title[:30])
+                    rendered_steps.append(s)
+                steps_to_use = rendered_steps
+            else:
+                # fallback: 硬编码 steps（向后兼容）
+                steps_to_use = [
                     f"在开发目录执行 git 操作：\n  a. git checkout main && git pull origin main\n  b. git checkout -b fix/{issue_number}-{brief}",
                     "编码 + 写 UT",
                     "文档同步：如果本次改动涉及设计变更或接口变更，在同一分支更新 docs/design/ 对应文档。如无需更新，在 action report 中说明「文档无需更新」",
@@ -1040,7 +1062,16 @@ async def _handle_issues(payload: Dict[str, Any]) -> None:
                     f"CI 通过后创建 PR（Gitea API: POST /repos/{repo}/pulls，head: fix/{issue_number}-{brief}, base: main）— PR body 必须含 Closes #{issue_number}",
                     "等 Review",
                     "提交 action report（POST http://localhost:8083/api/projects/_toolchain/tasks/<task_id>/comments，comment_type=action_report）— 报告中必须说明文档是否需要更新及处理结果",
-                ],
+                ]
+
+            title = f"Issue 指派: {issue_title} ({repo}#{issue_number})"
+            _send_toolchain_task(
+                to_agent=assignee,
+                title=title,
+                description=text,
+                event_type="issue_assigned",
+                action_type="issue_assigned",
+                steps=steps_to_use,
                 context_data={
                     "issue_number": issue_number,
                     "repo": repo,
@@ -1048,9 +1079,30 @@ async def _handle_issues(payload: Dict[str, Any]) -> None:
                     "labels": labels,
                     "issue_body": issue_body or "(无描述)",
                     "brief": brief,
+                    "business_type": business_type,
                 },
             )
 
+    elif action == "closed":
+        # §21 §11 Issue closed 纯通知（auto-pass）
+        assignee_login = ""
+        issue_assignees = issue.get("assignees") or []
+        if issue_assignees:
+            assignee_login = issue_assignees[-1].get("login", "")
+        if not assignee_login or assignee_login not in AGENT_IDS:
+            logger.debug("Issue closed but no valid assignee, skipping")
+            return
+        title = f"Issue 已关闭: {issue_title} ({repo}#{issue_number})"
+        _send_toolchain_task(
+            to_agent=assignee_login,
+            title=title,
+            description=f"## Issue 已关闭\n\n**{repo}#{issue_number}**: {issue_title}\n\nIssue 已被关闭。",
+            event_type="issue_closed",
+            action_type="issue_closed",
+            steps=[],  # 纯通知，无步骤
+            context_data={"repo": repo, "issue_number": issue_number},
+        )
+
     elif action == "opened":
         if "部署失败" in issue_title:
             # 从 Issue body 提取 commit hash（Gitea deploy workflow 格式）