fix(skill_engine): parse block scalars without requiring PyYAML

openspace/skill_engine/skill_utils.py

@@ -113,15 +113,30 @@ def get_frontmatter_field(content: str, field_name: str) -> Optional[str]:
     """Extract a single field value from YAML frontmatter.
 
     Returns ``None`` if the field is absent or content has no frontmatter.
-    Uses :func:`parse_frontmatter` so block scalars (``|`` / ``>``) round-trip.
+    Block scalars (``|`` / ``>``) include following indented lines.
     """
-    fm = parse_frontmatter(content)
-    if field_name not in fm:
+    if not content.startswith("---"):
         return None
-    value = fm[field_name]
-    if value is None:
+    match = _FRONTMATTER_RE.match(content)
+    if not match:
         return None
-    return value if isinstance(value, str) else str(value)
+    lines = match.group(1).split("\n")
+    for i, line in enumerate(lines):
+        if ":" not in line:
+            continue
+        key, value = line.split(":", 1)
+        if key.strip() != field_name:
+            continue
+        rest = value.strip()
+        if re.fullmatch(r"[|>][+-]?", rest):
+            collected: List[str] = []
+            j = i + 1
+            while j < len(lines) and lines[j].startswith((" ", "\t")):
+                collected.append(re.sub(r"^[ \t]+", "", lines[j], count=1))
+                j += 1
+            return "\n".join(collected)
+        return _yaml_unquote(rest)
+    return None
 
 
 def set_frontmatter_field(content: str, field_name: str, value: str) -> str:

tests/skill_engine/test_get_frontmatter_block_scalar.py

@@ -10,6 +10,16 @@ def test_get_frontmatter_field_reads_block_scalar_description():
     assert get_frontmatter_field(src, "description") == "line1\nline2"
 
 
+def test_get_frontmatter_field_reads_folded_scalar():
+    src = "---\nname: x\ndescription: >\n  line1\n  line2\n---\n"
+    assert get_frontmatter_field(src, "description") == "line1\nline2"
+
+
 def test_get_frontmatter_field_missing_returns_none():
     src = "---\nname: x\n---\n"
     assert get_frontmatter_field(src, "description") is None
+
+
+def test_get_frontmatter_field_keeps_plain_scalar_text():
+    src = "---\nenabled: true\n---\n"
+    assert get_frontmatter_field(src, "enabled") == "true"