feat(beaver): 完成Task Team功能v1实现，重构后端架构支持统一内核

新增内部Task系统，包括验证、反馈门控机制，实现自动质量验证
(通过率>=0.75)和用户反馈闭环(satisfied/revise/abandon)。

实现Agent Team v1协调器，支持sequence/parallel/dag执行策略，
sub-agent复用主AgentLoop，每个run使用独立memory snapshot。

建立Skill学习pipeline，包含draft/审核/发布/回滚完整生命周期，
通过Task验证通过且用户满意才生成学习候选。

重构目录结构，移除third_party依赖，建立统一engine内核，
所有agent共享运行时基础组件。

更新ContextBuilder清理provider消息字段，增强SkillContext版本管理，
集成TaskExecutionPlanner和TaskSkillResolver实现技能解析机制。

app-instance/backend/beaver/skills/reviews/service.py

@@ -0,0 +1,76 @@
+"""Review workflow for Beaver skill drafts."""
+
+from __future__ import annotations
+
+from uuid import uuid4
+
+from beaver.skills.specs import SkillDraft, SkillReviewRecord, SkillReviewState, SkillSpecStore
+
+
+class ReviewService:
+    def __init__(self, store: SkillSpecStore) -> None:
+        self.store = store
+
+    def submit_for_review(self, skill_name: str, draft_id: str, reviewer_request: str, requested_by: str = "system") -> SkillReviewRecord:
+        draft = self._require_draft(skill_name, draft_id)
+        draft.status = SkillReviewState.IN_REVIEW.value
+        self.store.write_draft(draft)
+        review = SkillReviewRecord(
+            review_id=uuid4().hex,
+            draft_id=draft_id,
+            skill_name=skill_name,
+            requested_at=_utc_now(),
+            requested_by=requested_by,
+            status=SkillReviewState.IN_REVIEW.value,
+            notes=reviewer_request,
+        )
+        self.store.write_review(review)
+        return review
+
+    def approve(self, skill_name: str, draft_id: str, reviewer: str, notes: str = "") -> SkillReviewRecord:
+        draft = self._require_draft(skill_name, draft_id)
+        draft.status = SkillReviewState.APPROVED.value
+        self.store.write_draft(draft)
+        review = SkillReviewRecord(
+            review_id=uuid4().hex,
+            draft_id=draft_id,
+            skill_name=skill_name,
+            requested_at=_utc_now(),
+            requested_by=reviewer,
+            status=SkillReviewState.APPROVED.value,
+            reviewer=reviewer,
+            reviewed_at=_utc_now(),
+            notes=notes,
+        )
+        self.store.write_review(review)
+        return review
+
+    def reject(self, skill_name: str, draft_id: str, reviewer: str, notes: str = "") -> SkillReviewRecord:
+        draft = self._require_draft(skill_name, draft_id)
+        draft.status = SkillReviewState.REJECTED.value
+        self.store.write_draft(draft)
+        review = SkillReviewRecord(
+            review_id=uuid4().hex,
+            draft_id=draft_id,
+            skill_name=skill_name,
+            requested_at=_utc_now(),
+            requested_by=reviewer,
+            status=SkillReviewState.REJECTED.value,
+            reviewer=reviewer,
+            reviewed_at=_utc_now(),
+            notes=notes,
+        )
+        self.store.write_review(review)
+        return review
+
+    def _require_draft(self, skill_name: str, draft_id: str) -> SkillDraft:
+        draft = self.store.read_draft(skill_name, draft_id)
+        if draft is None:
+            raise ValueError(f"Draft not found: {skill_name}/{draft_id}")
+        return draft
+
+
+def _utc_now() -> str:
+    from datetime import datetime, timezone
+
+    return datetime.now(timezone.utc).isoformat()