Codeblock Fence Test

Goal

Add a regression test for triple-backtick code block autoformat behavior.

Context

• User asked for a test around ``` not autoformatting to a code block.
• The likely owner is the code-block input-rule path, not docs UI.
• Existing learnings point to block-fence input rules as the correct seam.

Relevant Learnings

• docs/solutions/best-practices/block-fence-input-rules-should-split-fence-matching-from-feature-apply.md
• docs/solutions/best-practices/input-rules-should-register-explicit-rule-instances-while-packages-export-markdown-families.md

Working Plan

• Load skills and scan relevant learnings
• Find the narrowest existing code-block/input-rule test seam
• Add a regression test for triple-backtick promotion
• Run the targeted test
• Decide whether the same turn should carry the fix

Findings

• The core package already had a direct input-rule test in packages/code-block/src/lib/BaseCodeBlockPlugin.inputRules.spec.tsx.
• The missing coverage was the shipped app kit surface. CodeBlockKit is the right owner lane because it wires CodeBlockRules.markdown({ on: 'match' }) into the registry editor surface.
• Added app package-integration coverage instead of another core-only test.
• The new regression test passes, so this turn did not need a fix. The request was satisfied by locking the contract where regressions are likely to sneak in.