Remove decorative food window-frame mode

[tamirelazar]

Removes the decorative food window-frame mode (a green border with zero simulation effect, whose name misleads users into expecting food-source behavior). Confirmed purely decorative by the ws5 frame-mode spike.

This does not touch the real image-based food feature (--init food / InitMode::Food / food.rs), which is untouched.

Changes

• Remove WindowFrame::Food variant, its thickness() arm, render_food(), and both FromStr parse arms (config.rs + config_manager.rs)
• Relink the window-frame cycle ring to skip Food (forward Reactive→Frame, reverse Frame→Reactive); ring stays complete over None/Negative/Accented/Glow/Reactive/Frame
• Drop food from the --window-frame help and FromStr error message

Related

• ws5 frame-mode assessment. Frame-containment nit tracked separately in Window-frame: sim content leaks outside inset frame in 'frame' mode #26.

Test plan

• cargo test (758 lib + 46 visual regression), cargo test --all-features --lib (770), cargo clippy -D warnings, cargo fmt — all clean
• Manual: cycling window frame ( ( / ) ) no longer stops on a food border; reaches all 6 remaining modes