[Feature Request] Allow custom background color configuration for user input

Bug Description
ユーザー入力の背景色を個別にカスタマイズしたい

Environment Info

• Platform: darwin
• Terminal: WarpTerminal
• Version: 2.1.42
• Feedback ID: 5ef5f49e-3630-43f0-a3bc-739cfa3436ff

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/leapsec/.local/share/claude/versions/2.1.42 (expected in multi-process scenarios)\n    at ZwR (/$bunfs/root/claude:3483:2098)\n    at ESA (/$bunfs/root/claude:3483:1209)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-02-14T01:00:50.447Z"}]