feat(cli): port ghostty +action CLI commands

Ports ZIG/src/cli into ghostty-cli: action detection/dispatch with
per-action --help, and the actions help, version, list-actions,
list-colors, list-keybinds, list-themes (plain listing plus an
interactive ratatui browser mirroring Ghostty's libvaxis UI),
show-config, validate-config, edit-config, crash-report (listing),
ssh-cache and boo (235 embedded frames).

Verified byte-for-byte against the installed Ghostty 1.3.1 for stdout,
stderr and exit codes of most actions, incl. tty output in a pty at
widths 20-200. Known differences: +list-colors --plain prints all 782
colors (Ghostty truncates at 617 because it never flushes), +version
has placeholder build info until build_info::set is wired up.

Deferred: list-fonts, show-face (need font discovery integration) and
new-window (needs GTK IPC); they return NotYetAvailable for now.

Test Plan:
- cargo test -p ghostty-cli (86 tests)
- cargo run -p ghostty-cli --example cli -- +list-keybinds --plain
  and diff against `ghostty +list-keybinds --plain`

crates/ghostty-cli/examples/cli.rs

@@ -0,0 +1,14 @@
+//! End-to-end runner for the CLI actions:
+//! `cargo run -p ghostty-cli --example cli -- +list-actions --docs`
+//!
+//! Behaves like `ghostty` when an action is given (including `--version`,
+//! `--help` and `-h`), and otherwise prints a note.
+
+fn main() {
+    let args: Vec<String> = std::env::args().collect();
+    if let Some(code) = ghostty_cli::run_from_args(&args) {
+        std::process::exit(i32::from(code));
+    }
+    eprintln!("no +action given (this example only runs CLI actions)");
+    std::process::exit(2);
+}