refactor: resolve cross-crate integration TODOs and resources discovery

Cleanup pass over items collected in docs/rewrite/INTEGRATION_TODO.md:
- OSC 133 printf-q / percent decoders live once in
  ghostty_vt::string_encoding; ghostty-os re-exports them.
- CursorStyle and clipboard codepoint map entries have one definition
  (ghostty-terminal); ghostty-config now depends on ghostty-terminal.
- ActionKey::docs() trailing blank lines fixed at the source; cli's
  workaround removed (+list-actions --docs still byte-identical).
- x11_color exposes names in original case; cli no longer re-parses
  rgb.txt.
- One cgroup scope wait loop (ghostty_os::cgroup::wait_for_scope).
- Flatpak passwd lookup implemented in ghostty-os via a local pty.
- +version shows the rustc version captured at build time.

Resources: dev builds find <workspace>/resources automatically (keeping
Ghostty's sentinel-file detection and GHOSTTY_RESOURCES_DIR);
scripts/gen-terminfo.sh (just terminfo) regenerates the compiled
terminfo; `just install [PREFIX]` installs binary, share/ghostty,
terminfo, desktop/D-Bus/systemd/metainfo files and icons.

Test Plan:
- cargo test for vt, os, config, input, cli
- diff `+list-keybinds`, `+list-actions --docs`, `+show-config --default`
  against /usr/bin/ghostty

crates/ghostty-vt/src/lib.rs

@@ -17,6 +17,7 @@ pub mod parser;
 pub mod sgr;
 pub mod simd;
 pub mod stream;
+pub mod string_encoding;
 pub mod tmux;
 pub mod utf8_decoder;
 pub mod x11_color;