Summary

• keep single-paragraph Markdown find-replace fragments inside the existing paragraph
• preserve explicit terminal newlines and block Markdown behavior
• add regression coverage for inline and explicit-newline replacements

Verification

• focused Docs find-replace tests
• autoreview clean
• make ci
• live disposable Google Doc: two successive Markdown replacements produced exact paragraph spacing on raw readback; document trashed afterward

Closes #736

Thanks @sebsnyk.