Skills/Python: harden script edge cases and add regression tests (#24277)

* Skill creator: skip self-including .skill output

* Skill creator tests: cover output-dir-inside-skill case

* Skill validator: parse frontmatter robustly across newlines

* Skill validator tests: add CRLF and malformed frontmatter coverage

* Model usage: require positive --days value

* Model usage tests: cover --days validation and filtering

* Nano banana: close input image handles after loading

* Skill validator: keep type hints compatible with older python

* Changelog: credit @vincentkoc for Python skills hardening

skills/skill-creator/scripts/package_skill.py

@@ -93,6 +93,10 @@ def package_skill(skill_path, output_dir=None):
                     if not _is_within(resolved_file, skill_path):
                         print(f"[ERROR] File escapes skill root: {file_path}")
                         return None
+                    # If output lives under skill_path, avoid writing archive into itself.
+                    if resolved_file == skill_filename.resolve():
+                        print(f"[WARN] Skipping output archive: {file_path}")
+                        continue
 
                     # Calculate the relative path within the zip.
                     arcname = Path(skill_name) / file_path.relative_to(skill_path)