Draft: Add stash options to staging panel #5683

[nlvratna]

Prototype for Issue #5683: Add stash options to staging panel

Note: I have read CONTRIBUTING.md and understand that this project does not merge community PRs. As suggested in the contributing guidelines, I am opening this as a Draft PR to share a working prototype for anyone who might find it useful for their own forks, or in case the logic is helpful for a future official implementation.

What this does

This maps the standard stash options menu to the staging_controller.go local keybindings. It solves the issue by allowing users to trigger stash actions (like stashing only staged changes) directly from the Staging panel without needing to press Esc to drop back to the Files panel first.

Implementation Details

• Reused the existing stashOptions menu from the files controller.
• Mapped to the standard stash keybinding within the staging context.
• Verified locally that it successfully triggers git stash push --staged when selecting the staged changes option.