fix(skills): preserve version strings across markdown saves

tests/test_skill_version_preservation.py

@@ -0,0 +1,59 @@
+"""Issue #2131: editing a skill must not reinterpret its version as a number."""
+
+import pytest
+
+from services.memory.skill_format import Skill, parse_frontmatter
+from services.memory.skills import SkillsManager
+
+
+@pytest.mark.parametrize(
+    "raw, expected",
+    [
+        ("1.10", "1.10"),
+        ("2.20", "2.20"),
+        ("01", "01"),
+        ("0", "0"),
+        ("1.0.0", "1.0.0"),
+        ("true", "true"),
+        ("null", "null"),
+        ('"1.10"', "1.10"),
+        ("'2.20'", "2.20"),
+        ('"release\\u002d01"', "release-01"),
+    ],
+)
+def test_version_survives_repeated_markdown_saves(raw, expected):
+    markdown = f"---\nname: demo\nversion: {raw}\nconfidence: 0.80\n---\n"
+    for _ in range(3):
+        skill = Skill.from_markdown(markdown)
+        assert skill.version == expected
+        assert skill.confidence == 0.8
+        markdown = skill.to_markdown()
+
+
+def test_version_preservation_keeps_other_frontmatter_types():
+    fm, _ = parse_frontmatter(
+        "---\nversion: 1.10\nconfidence: 0.80\nuses: 3\n"
+        "enabled: true\ntags: [one, two]\n---\n"
+    )
+    assert fm == {
+        "version": "1.10", "confidence": 0.8, "uses": 3,
+        "enabled": True, "tags": ["one", "two"],
+    }
+
+
+@pytest.mark.parametrize("version_line", ["", "version:\n", 'version: ""\n'])
+def test_missing_or_empty_version_retains_default(version_line):
+    skill = Skill.from_markdown(f"---\nname: demo\n{version_line}---\n")
+    assert skill.version == "1.0.0"
+
+
+def test_version_survives_unrelated_edits_on_disk(tmp_path):
+    manager = SkillsManager(str(tmp_path))
+    manager.add_skill(name="demo", version="1.10", owner="alice")
+    for i in range(3):
+        assert manager.update_skill("demo", {"description": f"Edit {i}"}, owner="alice")
+        stored = manager.load(owner="alice")
+        assert stored[0]["version"] == "1.10"
+        assert stored[0]["description"] == f"Edit {i}"
+    markdown = next((tmp_path / "skills").rglob("SKILL.md")).read_text(encoding="utf-8")
+    assert "version: 1.10\n" in markdown