Add zt terminal emulator

[midasdf]

Add zt

zt is a minimal, ultra-fast terminal emulator written in pure Zig.

Highlights

• 1,382 MB/s throughput, 3.5ms startup, 4.3MB RSS
• Single-threaded epoll event loop, pure Zig (no libc for fbdev backend)
• Dual backend: Linux framebuffer and X11/XCB
• 59,635 embedded glyphs (BDF parsed at comptime)
• Full VT parser with xterm-256color + TrueColor
• Cross-compiles to aarch64 with zig build -Dtarget=aarch64-linux

Added under the System tools section.