[chaliy]

What changed

Keep rendered Markdown safe when nested inline delimiters or adjacent IR nodes would otherwise combine into syntax the IR did not request. Redundant nested bold, italic, and strikethrough wrappers render once. Text beginning with ( is escaped after a bracketed node so a footnote reference cannot become an inline link that consumes later delimiters.

Why

The post-merge full fuzz run found a repeated-bold case that closed its outer span before a block node and exposed code as raw HTML. A follow-up local run found the same output-safety failure when a footnote reference and following text combined into an inline link.

Before / After

• Before: redundant ** delimiters or [^x] followed by ( could consume later Markdown delimiters and expose code content as HTML in a downstream GFM renderer.
• After: both minimized crash artifacts replay successfully. Their exact inputs are retained as seeds and covered by output-safety regressions.
• just pre-pr: passed, including 51 output-safety tests and 119 HTML integration tests.
• Local render_ir fuzz: 500,715 inputs over 61 seconds with no crash.
• The committed tree is identical to the tree validated before moving this commit onto the merged main branch.

Risk

• Medium: redundant nested emphasis wrappers render once, and ( after a bracketed node may be escaped.
• Text and code content remain intact; no resource limits or security assertions are relaxed.

Checklist

• Tests added or updated
• Backward compatibility considered