docs(docs): expand terminal and tmux documentation with launch commands, prompts, persistence, and keybinding updates

docs/desktop/niri.mdx

@@ -433,7 +433,7 @@ Deployed to `~/.config/niri/scripts/`. `70-binds.kdl` binds none of them, so the
 | `kitty-CLASS` | exactly that class | `kitty --class kitty-CLASS` (optional command from the empty `KITTY_CMDS` map) |
 | `ghostty` | `ghostty` | nothing, prints a message |
 | `browser` | `^(zen\|brave\|chromium\|firefox)` | `zen` |
-| `terminal` | `kitty\|alacritty\|ghostty` | `kitty` |
+| `terminal` | `kitty\|alacritty\|ghostty` | `xdg-terminal-exec` (the OS default terminal from `~/.config/xdg-terminals.list`) |
 | `ai` | `claude\|hermes` | `hermes desktop` |
 | anything else | exact app-id | the argument as a command |