Implement skill self-evolution and skill_manage flow (#1874)

* chore: ignore .worktrees directory

* Add skill_manage self-evolution flow

* Fix CI regressions for skill_manage

* Address PR review feedback for skill evolution

* fix(skill-evolution): preserve history on delete

* fix(skill-evolution): tighten scanner fallbacks

* docs: add skill_manage e2e evidence screenshot

* fix(skill-manage): avoid blocking fs ops in session runtime

---------

Co-authored-by: Willem Jiang <willem.jiang@gmail.com>

backend/tests/test_security_scanner.py

@@ -0,0 +1,17 @@
+from types import SimpleNamespace
+
+import pytest
+
+from deerflow.skills.security_scanner import scan_skill_content
+
+
+@pytest.mark.anyio
+async def test_scan_skill_content_blocks_when_model_unavailable(monkeypatch):
+    config = SimpleNamespace(skill_evolution=SimpleNamespace(moderation_model_name=None))
+    monkeypatch.setattr("deerflow.skills.security_scanner.get_app_config", lambda: config)
+    monkeypatch.setattr("deerflow.skills.security_scanner.create_chat_model", lambda **kwargs: (_ for _ in ()).throw(RuntimeError("boom")))
+
+    result = await scan_skill_content("---\nname: demo-skill\ndescription: demo\n---\n", executable=False)
+
+    assert result.decision == "block"
+    assert "manual review required" in result.reason