Ignore a leading thematic break that isn't really frontmatter

[pcbeingused333]

The bug

Separator splits frontmatter from content with /\A---\s*(.*?)\s*---\s*(.*)/m. That regex also matches a post whose body starts with a --- thematic break and contains another ---:

---

An intro paragraph.

---

The rest of the post.

YAML.safe_load parses "An intro paragraph." to a String, so @frontmatter is a string, and Separator#frontmatter does @frontmatter.each { |key, value| ... }:

Perron::Resource::Separator.new("---\nintro\n---\nbody").frontmatter
# => NoMethodError: undefined method `each' for an instance of String

A YAML list between the fences is nearly as bad — it silently produces {item: nil, ...}.

The fix

Only treat the fenced block as frontmatter when it parses to a Hash (or to nil — empty frontmatter, already supported). Anything else means the leading --- was content.

Tests

Two cases added to separator_test.rb — a leading thematic break, and a bare scalar between the fences. Both fail on main (NoMethodError, and content mis-split). bundle exec rake is green (403 runs, 0 failures; standardrb clean).

🤖 Generated with Claude Code

[pcbeingused333]

CI is on action_required (fork gate). Verified with bundle exec rake (Docker, Ruby 3.4): 403 runs, 0 failures, standardrb clean. The two new tests fail on main (NoMethodError: undefined method 'each' for an instance of String).