* Polish chat input and sidebar interactions.
Standardize keyboard focus behavior and tighten sidebar and composer controls so the compact UI feels more consistent while preserving drag-and-drop image workflows.
* Fix lint follow-ups for UI polish.
Extract the chat image drop-target logic and tighten the shared focus selector so CI passes without changing the polished behavior.
* Fix keyboard focus detection for non-Tab navigation.
Preserve hidden pointer focus rings while restoring visible focus for keyboard shortcuts and other keyboard-driven flows that move focus without Tab.