Shell (!) mode: Tab should trigger normal terminal completion, not switch to Issues

Describe the feature or problem you'd like to solve

When executing a shell command directly by prefixing it with  ! , pressing Tab does not behave like a normal terminal's tab-completion (completing file/directory paths, commands, or flags). Instead, it switches focus/navigation to the Issues view within the CLI. This breaks the expected muscle-memory of a shell prompt and makes it harder to quickly complete paths or commands while working in  !  shell mode.

Proposed solution

When a command is prefixed with  !  (direct shell execution), pressing Tab currently gets intercepted by Copilot CLI's own UI (switching focus/view to Issues) instead of being passed through to the underlying shell for standard completion (file paths, commands, flags — like a normal terminal). Since  !  is meant to give a raw shell pass-through experience, Tab keystrokes while in that mode should be forwarded to the shell's native completion instead of being captured by the CLI's own keybindings.

Example prompts or workflows

1. In the Copilot CLI, type  !cd ../../projects/my-  and press Tab — expected: shell completes the path to the matching directory, same as typing it directly in a terminal.
2. Type  !git chec  and press Tab — expected: shell completes to  git checkout  (or cycles matches), not a switch to the Issues panel.
3. Type  !ls src/  and press Tab to cycle through files/folders in  src/  — expected: standard filename completion, same as bash/zsh/PowerShell.

Additional context

No response

Comienza siguiendo el manejo de Tab en el modo de shell ! y el keybinding que cambia a la vista Issues; el issue no especifica ningún archivo ni prueba. Verifica el comportamiento con los workflows de la ruta indicada, git checkout y la finalización de src/, y considera el trabajo terminado cuando Tab use la finalización normal de la shell subyacente en lugar de cambiar las vistas de la CLI.