Kitty graphics probe that works on macOS

Go cannot set a read deadline on a terminal device on macOS (kqueue does
not support them), so the probe failed at once and Ghostty and kitty got
block posters there. Wait for the answer with select(2) instead.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019reK4DUGYqDUjniWYJvwUW

go.mod

@@ -6,6 +6,7 @@ require (
 	github.com/gdamore/tcell/v2 v2.13.10
 	github.com/rivo/tview v0.42.0
 	golang.org/x/image v0.47.0
+	golang.org/x/sys v0.49.0
 	golang.org/x/term v0.37.0
 )
 
@@ -13,6 +14,5 @@ require (
 	github.com/gdamore/encoding v1.0.1 // indirect
 	github.com/lucasb-eyer/go-colorful v1.3.0 // indirect
 	github.com/rivo/uniseg v0.4.7 // indirect
-	golang.org/x/sys v0.49.0 // indirect
 	golang.org/x/text v0.43.0 // indirect
 )