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/seoulbones_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 = "#DDDDDD"
+background = "#4B4B4B"
+# Selection colors
+selection-foreground = "#DDDDDD"
+selection-background = "#777777"
+# Cursor colors
+cursor-color = "#E2E2E2"
+cursor-text = "#4B4B4B"
+# The basic 16 colors
+# black
+palette = 0=#4B4B4B
+palette = 8=#6C6465
+# red
+palette = 1=#E388A3
+palette = 9=#EB99B1
+# green
+palette = 2=#98BD99
+palette = 10=#8FCD92
+# yellow
+palette = 3=#FFDF9B
+palette = 11=#FFE5B3
+# blue
+palette = 4=#97BDDE
+palette = 12=#A2C8E9
+# magenta
+palette = 5=#A5A6C5
+palette = 13=#B2B3DA
+# cyan
+palette = 6=#6FBDBE
+palette = 14=#6BCACB
+# white
+palette = 7=#DDDDDD
+palette = 15=#A8A8A8