Cover the three things gui.sidePanels enables: reordering the panels
(swapping branches and commits, checked via their jump keys), hiding a
panel (omitting stash, checked by cycling past the last panel and wrapping
to the first), and promoting a tab to its own panel (worktrees becomes a
top-level panel reachable by a jump key, and the files panel's remaining
tabs cycle straight to submodules).
The tests drive focus with explicit jump keys rather than ViewDriver.Focus,
which assumes the default panel layout.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
