[iamnbutler]

Two leftovers from #36.

ace_image → image

• Renamed in the desktop_inspect, desktop_screen and desktop_menubar_click results: {width, height, note}.
• No legacy alias, because I found nothing external that reads it:
  • ace2's channel (packages/channel/src/desktop.ts), the only package that depends on desktop-tools, passes through the top-level image content and never parses ace_image.
  • Nothing else under ~/code mentions it, and the docs never did.
• Models see the field name only in result text.

No upscaling

• screenshot() used sips --resampleHeightWidthMax 1600, which enlarges anything smaller than that, such as a narrow display or any window under 1600 px.
• It now reads the source size first and caps each attempt at the source's longest side. Smaller sources are converted to JPEG without resampling. The 1200 and 800 retries for the 900 KB limit still apply, and still only shrink.
• The image notes now say "scaled down when large but never up".

Checked by running the built screenshot() on fixtures:

• 1000×600 PNG → 1000×600 JPEG (previously 1600×960).
• 3000×2000 → 1600×1066.

npm run check passes. No native changes.