Add on-screen feedback for the Shift copy-settings gesture, driven by a
single configurable color (visuals.toml [overlays].copy_config):
- eligible-target tint over every same-type building/site while a config
is cached (source included), shown only while a paste is possible;
- a brief selection-style outline flash on copy (source) and paste (target).
Flashes use a wall-clock countdown (frame delta), so they play for a fixed
0.3 s regardless of game speed and while paused, and fade independently per
building. Extract the footprint-rect resolution shared by the selection
highlight and the new feedback into footprintWidgetRect(). Pure rendering;
no simulation or selection state touched.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VGNNLeFWhVzvxkK9qVXP2K
