Add get_rich_menu and update_rich_menu_image tools

[4geru]

Summary

• Add get_rich_menu: fetch a single rich menu (size, chat bar text, tap areas) by ID — the starting point for cloning an existing menu definition
• Add update_rich_menu_image: replace the image of an existing rich menu via clone-and-replace, since the LINE Messaging API does not allow overwriting an already uploaded image
  • Flow: fetch old menu definition → validate image → create new menu with the same definition → upload new image (rolls back the new menu on failure) → take over the default assignment if the old menu was the default → delete the old menu (deleteOldRichMenu, default true)
  • A new richMenuId is issued and returned; the old one becomes invalid

Image validation (no new dependencies)

• Constraints stated in the tool/input schema descriptions: PNG/JPEG, width 800–2500px, height ≥250px, aspect ratio ≥1.45, max 1MB
• Dimensions are read by parsing the PNG IHDR / JPEG SOF headers directly
• Image dimensions must match the existing rich menu size; all validation errors are actionable (actual vs expected + what to do next), so an LLM caller can self-correct

Test plan

• 8 new test cases (happy path, default takeover on/off, deleteOldRichMenu=false, dimension mismatch, upload-failure rollback, no default set)
• npm test: 16 files / 50 tests passed