docs: explain Ghostty Option permission shortcuts

docs/installation.md

@@ -60,6 +60,52 @@ To locate data safely:
 
 For tests, explicitly set `MINIMAX_DATA_DIR` to a temporary directory to keep normal sessions separate. Use `$env:MINIMAX_DATA_DIR = 'C:\path\to\test-profile'` in PowerShell or `export MINIMAX_DATA_DIR=/path/to/test-profile` in a POSIX shell.
 
+## macOS terminal shortcuts: Ghostty Option+M
+
+In the composer, `Alt+M` (`Option+M` on macOS) cycles permission modes through Ask, Auto, and Full access. Its binding ID is `composer.cycle-permission`. `Shift+Tab` toggles **Plan mode**, a separate setting. You can also use `/permission` to choose a permission mode and `/permission status` to inspect it without an Option shortcut.
+
+If `Option+M` inserts `µ` instead, the terminal is sending text rather than the expected Alt shortcut. MCode preserves literal `µ` as text; it cannot safely infer a permission change from that character. The terminal must forward the modifier, or you can choose another binding.
+
+### Configure Ghostty's Option key
+
+Ghostty's [`macos-option-as-alt`](https://ghostty.org/docs/config/reference#macos-option-as-alt) default is **keyboard-layout dependent** when unset, not always `false`. The current reference lists U.S. Standard and U.S. International as defaulting to `true`; other layouts default to `false`. Check the active macOS input source and the configuration loaded by your installed Ghostty version.
+
+Set this in your Ghostty configuration to send both Option keys as Alt:
+
+```ini
+macos-option-as-alt = true
+```
+
+Use `left` or `right` instead of `true` to reserve only that Option key for shortcuts and retain Unicode composition on the other side. Use the configured side when testing `Option+M`.
+
+Follow Ghostty's [configuration locations and precedence](https://ghostty.org/docs/config#file-location): macOS-specific files load after XDG files, and later settings can override earlier ones. Inspect the loaded setting from the same Ghostty installation, without `--default`:
+
+```bash
+ghostty +show-config | awk '/^macos-option-as-alt[[:space:]]*=/'
+```
+
+If `ghostty` is not on `PATH`, use the executable inside your installed app bundle, typically `/Applications/Ghostty.app/Contents/MacOS/ghostty`. An empty or omitted value is not proof of `false`; unset behavior depends on the layout. After editing, reload Ghostty's configuration from its menu (default `Cmd+Shift+,`) and open a new terminal. This is separate from MCode's `/reload` command.
+
+### Keep Option for text and customize MCode instead
+
+While idle, open `/hotkeys`, select `composer.cycle-permission`, press `Enter`, press `Ctrl+X`, then press `Enter` to save. `Ctrl+X` is unused by the current default MCode bindings; check any custom terminal or multiplexer bindings too. Do not choose `Ctrl+M`: terminals commonly encode it identically to `Enter`.
+
+Alternatively, merge this entry into `<data-dir>/tui/keybindings.json`, preserving any existing entries:
+
+```json
+{
+  "composer.cycle-permission": "ctrl+x"
+}
+```
+
+For the default profile this is `~/.minimax/tui/keybindings.json`; [profiles and data-directory overrides](#accounts-and-data) change the path. Create the `tui` directory if needed. After editing the file, run `/reload` while idle with no pending interaction or queued message, or restart MCode. This replaces `Alt+M`; use `["alt+m", "ctrl+x"]` as the value to retain both bindings. `/hotkeys` shows the effective binding.
+
+### Verify the result
+
+With an idle composer and no open picker or permission prompt, note `/permission status`, press the configured shortcut, and check the status again. The mode should advance without inserting text. Restore your intended permission mode through `/permission` afterward. Confirm that `Shift+Tab` still toggles Plan mode and that pasting `µ` still inserts text.
+
+If it still fails, record `mcode --version`, Ghostty's version, active keyboard layout, which Option key you pressed, the setting above, the effective `/hotkeys` entry, and whether tmux or SSH is involved. Compare with a direct Ghostty session. MCode supports both legacy ESC-prefixed Alt input and extended keyboard reports; a shell's raw-key display alone does not establish what Ghostty sends after the TUI negotiates its keyboard protocol.
+
 ## Update or remove
 
 Save your changes, fetch a reviewed revision with Git, then repeat the frozen install and build. A source installation does not automatically become an official npm installation.