[thelastbackspace]

Description

Two fixes from #343.

The rule parser ended a section at any line starting with #, including lines inside a fenced code block. So a Description with a fenced example like # When Triggered got cut off at the fence, and the fenced line was read as the When Triggered section. parseSection and the Rule Editor form's sectionBlocks now both skip headings inside a closed fence (a small shared fencedLines helper in src/core/markdown-fences.ts), so they still read sections the same way. A fence marker that never closes doesn't count, so a stray ``` can't hide the rest of the rule.

Test Rule set its loading text with textContent on the element preact renders into. Preact doesn't own that text node, so it stayed above the result, and for a rule without thresholds the second run showed only the loading text. I render it through preact instead.

I updated the three tests that pinned the old behavior. The "heading inside the detect block" tests now open the detect block mid-line, which is the case where a heading inside it can still happen, so the read-only handling stays covered. None of the 45 built-in rules change.

Related Issues

Fixes #343

Checklist

• npm run check passes (typecheck + lint + spellcheck + knip + tests). The 8 failing tests also fail on main.
• Changes are covered by tests
• Documentation updated (not needed)