Investigate markdown delimiter hiding on CRLF

Issue

Markdown delimiter hiding may not trigger correctly when content contains CRLF line endings.

Context

The hideDelimiters extension rebuilds decorations on document and selection changes, but there may be edge cases with CRLF (\r\n) where the syntax tree isn't updated correctly, causing delimiters to remain visible or hidden incorrectly.

Previous work

Commit bae7ba4 mentions "Fix CRLF delimiter hiding by explicitly rebuilding decorations on Enter" - this may need further investigation.

To investigate

• Test delimiter hiding behavior with CRLF vs LF line endings
• Check if Enter key creates CRLF on some platforms
• Verify syntax tree updates correctly after newline insertion