fix: escape unusual paths in Markdown plans

[rogerchappel]

Summary

• render every Markdown path as a JSON string literal in an inline code span
• adapt the code-span fence to filenames containing backticks
• keep control characters escaped so each file remains one Markdown list item
• preserve exact path values in JSON output and document the display convention

Commits

• 05ec4e1 test: cover Markdown-safe unusual paths
• a8ad823 fix: escape paths in Markdown plans
• 119f294 docs: explain Markdown path escaping

Verification

• npm run release:check
• git diff --check origin/main...HEAD
• git log --format="%h%x09%an%x09%ae%x09%cn%x09%ce" origin/main..HEAD (all commits: Roger Chappel miscanalysis@gmail.com)