```

feat(learning): 添加技能学习候选者合成锁定机制

添加了 DraftSynthesisInProgress 和 DraftHasNoChanges 异常来处理并发场景，
确保同一技能学习候选者的合成过程不会重复执行。实现了 claim_learning_candidate_for_synthesis
方法来原子性地锁定候选者进行合成。

fix(web): 为技能草案创建端点添加适当的HTTP状态码

当草案没有变化或正在合成时，现在正确返回409状态码而不是内部错误。

feat(skills): 实现技能修订内容比较以检测无变化情况

添加了 _is_noop_revision 方法来比较基础技能和提议的修订，
如果内容没有实际变化则抛出 NoDraftChanges 异常。

refactor(process): 修复任务证据记录后根运行状态更新逻辑

将任务证据记录事件后的状态从 waiting 更改为 done，并设置 finished_at 时间戳。

feat(tools): 防止在同一运行中重复执行外部写入操作

为邮件发送、日历创建等外部写入工具添加去重机制，避免重复的外部操作。

test: 添加技能学习和工具执行的单元测试

增加测试用例验证并发草案合成、重复外部写入抑制和无变化修订检测等功能。
```

app-instance/backend/beaver/interfaces/web/app.py

@@ -52,7 +52,13 @@ from beaver.services.user_file_resolver import (
 )
 from beaver.skills.authoring import canonical_skill_format_instructions, ensure_canonical_skill_body, normalize_skill_frontmatter
 from beaver.skills.authoring.format import parse_skill_rewrite_json
-from beaver.skills.learning import SkillLearningService, SkillLearningWorker, SkillLearningWorkerConfig
+from beaver.skills.learning import (
+    DraftHasNoChanges,
+    DraftSynthesisInProgress,
+    SkillLearningService,
+    SkillLearningWorker,
+    SkillLearningWorkerConfig,
+)
 from beaver.skills.learning.replay import ReplayRunner
 from beaver.skills.catalog.utils import extract_required_tool_names, parse_frontmatter
 
@@ -2236,6 +2242,10 @@ def create_app(
                 candidate_id,
                 provider_bundle=provider_bundle,
             )
+        except DraftHasNoChanges as exc:
+            raise HTTPException(status_code=409, detail=str(exc)) from exc
+        except DraftSynthesisInProgress as exc:
+            raise HTTPException(status_code=409, detail=str(exc)) from exc
         except ValueError as exc:
             raise HTTPException(status_code=404, detail=str(exc)) from exc
         return _skill_draft_payload(loaded, draft.skill_name, draft.draft_id)
@@ -2251,6 +2261,10 @@ def create_app(
                 candidate_id,
                 provider_bundle=provider_bundle,
             )
+        except DraftHasNoChanges as exc:
+            raise HTTPException(status_code=409, detail=str(exc)) from exc
+        except DraftSynthesisInProgress as exc:
+            raise HTTPException(status_code=409, detail=str(exc)) from exc
         except ValueError as exc:
             raise HTTPException(status_code=404, detail=str(exc)) from exc
         return _skill_draft_payload(loaded, draft.skill_name, draft.draft_id)