Small Fix, shade set freedom in threadExit

[pressatojump]

What do you want to change?

Just trying to use this on my mac and noticed every closed terminal leaks its GPU shader set (5 render pipelines + the shader library). in src/renderer/generic.zig " threadExit" it only frees when the display was unrealized — and only the GTK app ever does that. Just made a small fix 7 lines and changes nothing on GTK.

Why do you want to make this change?

Profiling it against iTerm--Ghostty is awesome, just want it to run clean on mac even though it already runs super lean.

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[jcollie]

!vouch