v0.19.0 — markdown API for page edit, export, backup, and comments

What's new

Added

• page edit --find/--replace-text — search-and-replace within a page via native markdown API. Single PATCH call, no block position calculations. --replace-all replaces all occurrences.

  notion page edit <id> --find "DRAFT" --replace-text "FINAL"
  notion page edit <id> --find "old text" --replace-text "new text" --replace-all

• comment create --markdown — create comments with markdown formatting.

  notion comment create --page <id> --text "**bold** and [link](url)" --markdown

Changed

• export page / export database --content — use native markdown API instead of recursive block fetching. Eliminates N+1 calls.
• backup --format markdown — uses native markdown API per page; --content flag required (same as JSON format).

Fixed

• Indentation in page edit block-level code path.
• Tests added for --find/--replace-text (basic, --replace-all, --dry-run, missing flag error).