In Ghostty, Alacritty and Terminal.app, Settings says plainly what won't work and what to use #445

Context

In Ghostty, Alacritty and Terminal.app, Settings → Terminal says "No integration available for this terminal yet", which suggests one is coming. None can be done properly: Alacritty's bindings are global, Ghostty has no per-program bindings and its pass-through arrives as a Super key TuiCode can't see, and Terminal.app is off-vision. The vision asks us to be honest about the terminal, so the panel says what won't work and what to use instead. Needs #444, which also changes this panel. Part of #40.

Acceptance criteria

• In Alacritty, Settings → Terminal shows Detected terminal: Alacritty, says Cmd+C/Cmd+X can't reach TuiCode without breaking copy in the shell, says to use Ctrl+C/Ctrl+X inside TuiCode and that Cmd+V pastes as usual, and recommends iTerm2, WezTerm or kitty for Cmd keys. No Buttons.
• Ghostty shows the same shape with its own reason (no per-program key bindings).
• Terminal.app shows the same shape with its own reason (it doesn't pass the modifiers TuiCode needs).
• Any other unrecognised terminal still shows today's "No integration available" text, listing kitty among the supported terminals.

Tests

• Panel state for each of the three terminals and for an unknown one, driven by their environment variables.

Out of scope

• Any key remapping for these terminals.
• The tmux note (Copy and cut over SSH reach my laptop's clipboard #443).
• Linux and Windows terminals.