feat(skill-learning): merge plugin skill updates

app-instance/backend/beaver/skills/learning/preservation.py

@@ -32,6 +32,30 @@ def check_preservation(*, base_content: str, draft_content: str) -> dict[str, An
     }
 
 
+def check_plugin_merge_preservation(
+    *,
+    local_content: str,
+    upstream_content: str,
+    draft_content: str,
+    merge_decisions: dict[str, Any],
+) -> dict[str, Any]:
+    local = check_preservation(base_content=local_content, draft_content=draft_content)
+    upstream = check_preservation(base_content=upstream_content, draft_content=draft_content)
+    unresolved = [str(item) for item in merge_decisions.get("unresolved_conflicts") or []]
+    safety_sections_missing = _important_sections_missing(upstream, local)
+    passed = bool(local.get("passed")) and bool(upstream.get("passed")) and not unresolved and not safety_sections_missing
+    return {
+        "mode": "plugin_three_way",
+        "passed": passed,
+        "risk_level": "high" if not passed else "low",
+        "local": local,
+        "upstream": upstream,
+        "unresolved_conflicts": unresolved,
+        "safety_sections_missing": safety_sections_missing,
+        "resolved_conflicts": [str(item) for item in merge_decisions.get("resolved_conflicts") or []],
+    }
+
+
 def _sections(content: str) -> dict[str, str]:
     current = "body"
     sections: dict[str, list[str]] = {current: []}
@@ -51,3 +75,13 @@ def _sections(content: str) -> dict[str, str]:
 
 def _normalize(value: str) -> str:
     return re.sub(r"\s+", " ", value or "").strip().lower()
+
+
+def _important_sections_missing(*reports: dict[str, Any]) -> list[str]:
+    important = {"safety", "required tools", "required tool", "tools"}
+    missing: list[str] = []
+    for report in reports:
+        for section in report.get("dropped_sections") or []:
+            if str(section).strip().lower() in important and str(section) not in missing:
+                missing.append(str(section))
+    return missing