test(skill_utils): add regression tests for non-dict metadata in extract_skill_conditions

The fix for this bug (isinstance guard) was merged via commit 3ff9e010,
but test coverage was not included. Adding 4 tests:
- dict metadata with hermes keys (normal case)
- string metadata (bug case — previously caused AttributeError)
- None metadata
- missing metadata key

tests/agent/test_skill_utils.py

@@ -0,0 +1,58 @@
+"""Tests for agent/skill_utils.py — extract_skill_conditions metadata handling."""
+
+from agent.skill_utils import extract_skill_conditions
+
+
+def test_metadata_as_dict_with_hermes():
+    """Normal case: metadata is a dict containing hermes keys."""
+    frontmatter = {
+        "metadata": {
+            "hermes": {
+                "fallback_for_toolsets": ["toolset_a"],
+                "requires_toolsets": ["toolset_b"],
+                "fallback_for_tools": ["tool_x"],
+                "requires_tools": ["tool_y"],
+            }
+        }
+    }
+    result = extract_skill_conditions(frontmatter)
+    assert result["fallback_for_toolsets"] == ["toolset_a"]
+    assert result["requires_toolsets"] == ["toolset_b"]
+    assert result["fallback_for_tools"] == ["tool_x"]
+    assert result["requires_tools"] == ["tool_y"]
+
+
+def test_metadata_as_string_does_not_crash():
+    """Bug case: metadata is a non-dict truthy value (e.g. a YAML string)."""
+    frontmatter = {"metadata": "some text"}
+    result = extract_skill_conditions(frontmatter)
+    assert result == {
+        "fallback_for_toolsets": [],
+        "requires_toolsets": [],
+        "fallback_for_tools": [],
+        "requires_tools": [],
+    }
+
+
+def test_metadata_as_none():
+    """metadata key is present but set to null/None."""
+    frontmatter = {"metadata": None}
+    result = extract_skill_conditions(frontmatter)
+    assert result == {
+        "fallback_for_toolsets": [],
+        "requires_toolsets": [],
+        "fallback_for_tools": [],
+        "requires_tools": [],
+    }
+
+
+def test_metadata_missing_entirely():
+    """metadata key is absent from frontmatter."""
+    frontmatter = {"name": "my-skill", "description": "Does stuff."}
+    result = extract_skill_conditions(frontmatter)
+    assert result == {
+        "fallback_for_toolsets": [],
+        "requires_toolsets": [],
+        "fallback_for_tools": [],
+        "requires_tools": [],
+    }