feat(terminal): Align the terminal with IDEA's tabs, menu and settings

- ⌘T (Ctrl+Shift+T on Windows) opens a terminal tab while the terminal
  has focus; elsewhere the key keeps its IDE action.
- The tab bar's ▾ menu lists installed shells under "New Predefined
  Session" (login shell, shell integration) and links to Settings.
- Settings › Tools › Terminal: pick the shell path from the installed
  shells or browse for one, "Move focus to the Editor with Escape",
  fallback font, column width and a link to the Terminal keymap.

Claude-Session: https://claude.ai/code/session_01B65qLEKnkeYTGdbwhLpjCu

src-tauri/src/commands/mod.rs

@@ -184,6 +184,7 @@ pub fn builder() -> tauri_specta::Builder<tauri::Wry> {
         term::term_resize,
         term::term_kill,
         term::term_default_shell,
+        term::term_available_shells,
         run::run_configs,
         run::run_save_configs,
         run::run_start,

src-tauri/src/commands/term.rs

@@ -54,3 +54,10 @@ pub fn term_kill(state: State<'_, AppState>, id: TerminalId) -> IdeResult<()> {
 pub fn term_default_shell() -> String {
     ide_terminal::default_shell_path()
 }
+
+/// Installed shells for the Terminal's "New Predefined Session" menu.
+#[tauri::command]
+#[specta::specta]
+pub fn term_available_shells() -> Vec<String> {
+    ide_terminal::available_shells()
+}