[C] feat(icon): swap to new logo (gradient terminal squircle)

Designer delivered a redesigned logo: light-on-dark terminal squircle
with a chunky `>_` glyph instead of the original pixel `D_`. Visually
heavier, fills the canvas tighter, reads better at small sizes (the
Dock thumbnail and menubar status are both <40pt).

Source: 1000×1000 PNG. Below the macOS 1024×1024 recommendation, so
the 512@2x slice (1024×1024) gets a 2.4% upscale via sips. Visible
softness on Retina is minimal but real; if it ever bothers anyone,
ask the designer to bump the source to 1024+.

Pipeline same as before: PIL trims any transparent border, scripts/
make-icon.sh sips into the 10 required sizes, iconutil compiles
AppIcon.icns. Smoke-tested locally — build-app.sh produces a 39MB
universal Island.app with the new icon embedded, codesign --verify
passes ad-hoc.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 2 people