Add a drop-in `ssh` wrapper that sets up the remote environment for Ghostty. Anything not consumed as one of our own flags is forwarded to the real, wrapped `ssh` binary. It can be used directly (`ghostty +ssh user@host`), aliased (`alias ssh='ghostty +ssh --'`), or invoked through Ghostty's shell integration. Before exec'ing ssh, `+ssh`: - Forwards Ghostty environment to the remote (`--forward-env`): sets TERM=xterm-256color and requests SendEnv forwarding of COLORTERM, TERM_PROGRAM, and TERM_PROGRAM_VERSION. - Installs Ghostty's terminfo on the remote (`--terminfo`), informed by our existing `ssh-cache` system and using our internal xterm-ghostty terminfo representation. A third flag, `--cache`, controls cache use; `--cache=false` bypasses both read and write, which is useful for scripting and for debugging install failures without polluting the cache. For shell integration, this replaces the per-shell logic (which made up roughly a third of our shell integration scripts) with a simple wrapper function that translates GHOSTTY_SHELL_FEATURES into a `ghostty +ssh` command line.