feat(dist): generate completions, editor syntax, man pages, translations

Ports Ghostty's build-data helpers (main_build_data.zig, src/extra/*,
build/mdgen) as the ghostty-build-data binary: bash/zsh/fish
completions, Vim syntax/ftdetect/ftplugin/compiler, Sublime syntax (also
used by bat), terminfo source and ghostty(1)/ghostty(5) markdown. With
the version set to the installed 1.3.1-arch2, all generated files are
byte-identical to the installed Ghostty's.

- `just docs` renders man pages and HTML with pandoc.
- po/: Ghostty's 29 translation catalogs; `just locales` compiles them
  into the com.mitchellh.ghostty gettext domain.
- `just install PREFIX FLATPAK SYSTEM_PACKAGE` installs everything incl.
  terminfo text/termcap outputs and mirrors GhosttyResources.zig install
  modes (Flatpak D-Bus template without systemd; lib/systemd/user for
  system packages).
- Build metadata (version, tip/stable channel, commit, build mode) is
  derived at build time like build_config.zig; GTK/libadwaita
  compile-time versions come from pkg-config instead of constants.

Test Plan:
- cargo run -p ghostty-build-data -- +bash | diff - \
  /usr/share/bash-completion/completions/ghostty (same for zsh/fish/vim)
- just install /tmp/prefix

crates/ghostty-build-data/src/chunks_vim.rs

@@ -0,0 +1,74 @@
+// Generated from the Zig multiline strings of extra/vim.zig. Do not edit.
+pub const C0: &str = r####"" Vim filetype detect file
+" Language: Ghostty config file
+" Maintainer: Ghostty <https://github.com/ghostty-org/ghostty>
+"
+" THIS FILE IS AUTO-GENERATED
+
+au BufRead,BufNewFile */ghostty/config,*/*.ghostty/config,*/ghostty/themes/*,*.ghostty setf ghostty
+"####;
+pub const C1: &str = r####"" Vim filetype plugin file
+" Language: Ghostty config file
+" Maintainer: Ghostty <https://github.com/ghostty-org/ghostty>
+"
+" THIS FILE IS AUTO-GENERATED
+
+if exists('b:did_ftplugin')
+  finish
+endif
+let b:did_ftplugin = 1
+
+setlocal commentstring=#\ %s
+setlocal iskeyword+=-
+
+" Use syntax keywords for completion
+setlocal omnifunc=syntaxcomplete#Complete
+
+let b:undo_ftplugin = 'setl cms< isk< ofu<'
+
+if !exists('current_compiler')
+  compiler ghostty
+  let b:undo_ftplugin .= " makeprg< errorformat<"
+endif
+"####;
+pub const C2: &str = r####"" Vim compiler file
+" Language: Ghostty config file
+" Maintainer: Ghostty <https://github.com/ghostty-org/ghostty>
+"
+" THIS FILE IS AUTO-GENERATED
+
+if exists("current_compiler")
+  finish
+endif
+let current_compiler = "ghostty"
+
+CompilerSet makeprg=ghostty\ +validate-config\ --config-file=%:S
+CompilerSet errorformat=%f:%l:%m,%m
+"####;
+pub const C3: &str = r####"" Vim syntax file
+" Language: Ghostty config file
+" Maintainer: Ghostty <https://github.com/ghostty-org/ghostty>
+"
+" THIS FILE IS AUTO-GENERATED
+
+if exists('b:current_syntax')
+  finish
+endif
+
+let b:current_syntax = 'ghostty'
+
+let s:cpo_save = &cpo
+set cpo&vim
+
+syn iskeyword @,48-57,-
+syn keyword ghosttyConfigKeyword"####;
+pub const C4: &str = r####"
+
+syn match ghosttyConfigComment /^\s*#.*/ contains=@Spell
+
+hi def link ghosttyConfigComment Comment
+hi def link ghosttyConfigKeyword Keyword
+
+let &cpo = s:cpo_save
+unlet s:cpo_save
+"####;