refactor: consolidate SKILL.md version regex into lib/skill_meta.py

The same `^version:\s*"([^"]+)"\s*$` regex (or a slight variant) was
duplicated across three files: render.py inline, test_plugin_contract.py
local helper, test_version_consistency.py local helper. A future change
to the SKILL.md frontmatter version format would have needed to update
three places without any compile-time pressure to keep them in sync.

New skills/last30days/scripts/lib/skill_meta.py provides:
- `_VERSION_RE` private compiled pattern (accepts double-quoted,
  single-quoted, or unquoted YAML version scalars per the widening
  landed in 997708a)
- `read_skill_version(skill_md_path: Path) -> str | None` helper that
  catches OSError + UnicodeDecodeError and returns None on miss

Callers updated:
- render.py::_skill_version now calls skill_meta.read_skill_version
  inside the SKILL.md fallback loop, returning `read_skill_version(...) or "?"`.
  Semantically equivalent to the old break-after-first-SKILL.md logic.
- test_plugin_contract.py and test_version_consistency.py import the
  helper instead of defining the regex inline. Both files use the
  established sys.path.insert pattern.

Added tests/test_skill_meta.py with 6 direct unit tests covering the
helper's full contract: missing file, undecodable bytes, no-version-line,
and all three quoting styles (double, single, unquoted). Previously the
helper was only exercised transitively through render._skill_version().

Added test_skill_md_uses_double_quoted_version to
test_version_consistency.py — the old per-test regex incidentally
asserted "this repo's SKILL.md uses double-quotes" by being strict;
the shared helper accepts all three styles, so the assertion is now
explicit instead of implicit.

Code-reviewed by ce-code-review (8 reviewers); safe_auto fixes applied
inline (rename to _VERSION_RE, group or-chain instead of generator,
docstring tightened, dropped unnecessary `from __future__ import
annotations`, tightened signature to Path-only).

Conftest.py refactor for the sys.path.insert duplication across ~20 test
files filed as issue #411 — out of scope for this PR (touches many
files, separate concern).

Test results: 23 passed in the affected test set (16 prior + 6 new
test_skill_meta tests + 1 new double-quote assertion). Full suite shows
same 13 pre-existing failures as main; zero new failures.

tests/test_plugin_contract.py

@@ -1,5 +1,5 @@
 import json
-import re
+import sys
 import tomllib
 import unittest
 from pathlib import Path
@@ -8,17 +8,19 @@ from pathlib import Path
 ROOT = Path(__file__).resolve().parents[1]
 SKILL_ROOT = ROOT / "skills" / "last30days"
 
+sys.path.insert(0, str(SKILL_ROOT / "scripts"))
+from lib.skill_meta import read_skill_version  # noqa: E402
+
 
 def _json(path: Path) -> dict:
     return json.loads(path.read_text(encoding="utf-8"))
 
 
 def _skill_version() -> str:
-    text = (SKILL_ROOT / "SKILL.md").read_text(encoding="utf-8")
-    match = re.search(r'^version:\s*"([^"]+)"\s*$', text, re.MULTILINE)
-    if not match:
+    version = read_skill_version(SKILL_ROOT / "SKILL.md")
+    if not version:
         raise AssertionError("SKILL.md version frontmatter not found")
-    return match.group(1)
+    return version
 
 
 class TestPluginContract(unittest.TestCase):

tests/test_skill_meta.py

@@ -0,0 +1,61 @@
+"""Direct unit tests for skill_meta.read_skill_version.
+
+Covers the helper's own contract independent of render._skill_version which
+exercises it transitively. Without these, regressions in error handling or
+regex coverage inside the helper could pass CI because render.py's fallback
+to "?" swallows the signal.
+"""
+
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+
+ROOT = Path(__file__).resolve().parents[1]
+sys.path.insert(0, str(ROOT / "skills" / "last30days" / "scripts"))
+from lib.skill_meta import read_skill_version  # noqa: E402
+
+
+class ReadSkillVersionTests(unittest.TestCase):
+    def setUp(self) -> None:
+        self._tmp = tempfile.TemporaryDirectory()
+        self.tmp_path = Path(self._tmp.name)
+
+    def tearDown(self) -> None:
+        self._tmp.cleanup()
+
+    def _write_skill_md(self, body: str) -> Path:
+        path = self.tmp_path / "SKILL.md"
+        path.write_text(body)
+        return path
+
+    def test_double_quoted_version(self) -> None:
+        path = self._write_skill_md('---\nname: x\nversion: "9.9.9"\n---\n')
+        self.assertEqual("9.9.9", read_skill_version(path))
+
+    def test_single_quoted_version(self) -> None:
+        path = self._write_skill_md("---\nname: x\nversion: '8.8.8'\n---\n")
+        self.assertEqual("8.8.8", read_skill_version(path))
+
+    def test_unquoted_version(self) -> None:
+        path = self._write_skill_md("---\nname: x\nversion: 7.7.7\n---\n")
+        self.assertEqual("7.7.7", read_skill_version(path))
+
+    def test_missing_file_returns_none(self) -> None:
+        self.assertIsNone(read_skill_version(self.tmp_path / "does-not-exist.md"))
+
+    def test_no_version_line_returns_none(self) -> None:
+        path = self._write_skill_md("---\nname: x\n---\n# body without version\n")
+        self.assertIsNone(read_skill_version(path))
+
+    def test_undecodable_bytes_returns_none(self) -> None:
+        # Bytes 128-255 don't form valid UTF-8 sequences; read_text() raises
+        # UnicodeDecodeError which the helper must catch.
+        path = self.tmp_path / "SKILL.md"
+        path.write_bytes(bytes(range(128, 256)))
+        self.assertIsNone(read_skill_version(path))
+
+
+if __name__ == "__main__":
+    unittest.main()

tests/test_version_consistency.py

@@ -1,4 +1,5 @@
 import re
+import sys
 import unittest
 from pathlib import Path
 
@@ -6,16 +7,31 @@ from pathlib import Path
 ROOT = Path(__file__).resolve().parents[1]
 SKILL_ROOT = ROOT / "skills" / "last30days"
 
+sys.path.insert(0, str(SKILL_ROOT / "scripts"))
+from lib.skill_meta import read_skill_version  # noqa: E402
+
 
 def _skill_version() -> str:
-    text = (SKILL_ROOT / "SKILL.md").read_text(encoding="utf-8")
-    match = re.search(r'^version:\s*"([^"]+)"\s*$', text, re.MULTILINE)
-    if not match:
+    version = read_skill_version(SKILL_ROOT / "SKILL.md")
+    if not version:
         raise AssertionError("SKILL.md version frontmatter not found")
-    return match.group(1)
+    return version
 
 
 class TestVersionConsistency(unittest.TestCase):
+    def test_skill_md_uses_double_quoted_version(self) -> None:
+        # The shared VERSION_RE in skill_meta.py accepts double-quoted,
+        # single-quoted, and unquoted YAML version scalars. This repo's
+        # SKILL.md must use the double-quoted form so the badge string stays
+        # deterministic and contributors don't accidentally introduce a
+        # quoting style that's harder for downstream tooling to parse.
+        text = (SKILL_ROOT / "SKILL.md").read_text(encoding="utf-8")
+        self.assertRegex(
+            text,
+            re.compile(r'^version:\s*"[^"]+"\s*$', re.MULTILINE),
+            msg="SKILL.md frontmatter version must use double-quoted form",
+        )
+
     def test_root_skill_header_matches_frontmatter_version(self) -> None:
         text = (SKILL_ROOT / "SKILL.md").read_text(encoding="utf-8")
         version = _skill_version()