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/tokyobones_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 = "#C0CAF5"
+background = "#1A1B26"
+# Selection colors
+selection-foreground = "#C0CAF5"
+selection-background = "#2C4075"
+# Cursor colors
+cursor-color = "#CED6F7"
+cursor-text = "#1A1B26"
+# The basic 16 colors
+# black
+palette = 0=#1A1B26
+palette = 8=#36384D
+# red
+palette = 1=#F77890
+palette = 9=#F98EA0
+# green
+palette = 2=#74DBCB
+palette = 10=#6DE5D3
+# yellow
+palette = 3=#E1B068
+palette = 11=#F2BA64
+# blue
+palette = 4=#7BA2F7
+palette = 12=#90AFFA
+# magenta
+palette = 5=#BB9BF7
+palette = 13=#C6ACFA
+# cyan
+palette = 6=#2BC4DE
+palette = 14=#74DBCB
+# white
+palette = 7=#C0CAF5
+palette = 15=#7E98EB