feat(skill-learning): merge plugin skill updates

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

@@ -94,6 +94,34 @@ class DraftService:
         self.store.write_draft(draft)
         return draft
 
+    def create_plugin_update_draft(
+        self,
+        *,
+        skill_name: str,
+        base_version: str,
+        proposed_content: str,
+        proposed_frontmatter: dict,
+        created_by: str,
+        reason: str,
+        provenance: dict,
+        evidence_refs: list[dict] | None = None,
+    ) -> SkillDraft:
+        draft = SkillDraft(
+            draft_id=uuid4().hex,
+            skill_name=skill_name,
+            base_version=base_version,
+            proposed_content=proposed_content,
+            proposed_frontmatter=dict(proposed_frontmatter),
+            created_at=_utc_now(),
+            created_by=created_by,
+            reason=reason,
+            evidence_refs=list(evidence_refs or []),
+            proposal_kind="plugin_skill_update",
+            provenance=dict(provenance),
+        )
+        self.store.write_draft(draft)
+        return draft
+
     def create_retire_proposal(
         self,
         *,