feat: add Ghostty terminal support (#225)

Add shipwright runner for Ghostty terminal emulator with example themes.

- Add ghostty.lua runner with Ghostty-specific color format
- Update init.lua to include ghostty in runner_files
- Add zenbones_dark and zenbones_light example themes

Ghostty uses a similar format to Kitty but with `=` separators and
`palette = N=COLOR` syntax for the 16 ANSI colors.

Tested and working with Ghostty terminal.

extras/ghostty/rosebones_dark

@@ -0,0 +1,37 @@
+# This file is auto-generated by shipwright.nvim
+# Ghostty color configuration
+# See: https://ghostty.org/docs/config/reference
+# Basic colors
+foreground = "#E1D4D4"
+background = "#1A1825"
+# Selection colors
+selection-foreground = "#E1D4D4"
+selection-background = "#523A39"
+# Cursor colors
+cursor-color = "#E7DDDD"
+cursor-text = "#1A1825"
+# The basic 16 colors
+# black
+palette = 0=#1A1825
+palette = 8=#3A3651
+# red
+palette = 1=#EB7193
+palette = 9=#F289A4
+# green
+palette = 2=#317490
+palette = 10=#358DAF
+# yellow
+palette = 3=#F6C074
+palette = 11=#F9CA8E
+# blue
+palette = 4=#9CCFD8
+palette = 12=#94DAE6
+# magenta
+palette = 5=#C4A7E7
+palette = 13=#CEB3EF
+# cyan
+palette = 6=#9CCFD8
+palette = 14=#94DAE6
+# white
+palette = 7=#E1D4D4
+palette = 15=#BF9B99