[Bug]: skill naming checker crashes on malformed YAML frontmatter

System Info

Platform-independent CI/checker behavior.

Reproduction

scripts/check_skill_naming_convention.py::load_frontmatter_name() calls yaml.safe_load() without handling yaml.YAMLError:

data = yaml.safe_load(m.group(1)) or {}

A skill or agent file with malformed YAML frontmatter therefore aborts the checker with a PyYAML traceback instead of producing a normal validation diagnostic and exit code 1.

Expected behavior

Malformed frontmatter should be reported as a checker violation so all offending files can be listed in one run.

Actual behavior

The first malformed YAML document raises and terminates the script.

Proposed fix

Catch yaml.YAMLError in frontmatter loading, return a diagnostic to the caller, and add a regression test proving main() reports the malformed file without crashing.

Start in scripts/check_skill_naming_convention.py at load_frontmatter_name() and trace how its result reaches main(). Reproduce the failure with a skill or agent file containing malformed YAML frontmatter, then add the regression test described in the issue. Done means main() reports the malformed file as a validation violation, continues checking other files, and exits with code 1 instead of raising a PyYAML traceback.