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_sublime.rs

@@ -0,0 +1,20 @@
+// Generated from the Zig multiline strings of extra/sublime.zig. Do not edit.
+pub const C0: &str = r####"%YAML 1.2
+---
+# See http://www.sublimetext.com/docs/syntax.html
+name: Ghostty Config
+file_extensions:
+  - ghostty
+scope: source.ghostty
+
+contexts:
+  main:
+    # Comments
+    - match: '^\s*#.*$'
+      scope: comment.line.number-sign.ghostty
+
+    # Keywords
+    - match: '\b("####;
+pub const C1: &str = r####")\b'
+      scope: keyword.other.ghostty
+"####;