Keep hover-only actions accessible on tablets

[banjerluke]

Human comments

Using bb on a 13" Boox Note Max tablet these days, which is pretty awesome. There are a few areas where I'm unable to perform commands in the UI due to lack of a mouse, though. This PR fixes that. (Re-submitted version of #2647)

What was wrong

Several actions were revealed only on hover, while touch fallbacks were restricted to compact viewport widths. Tablets using desktop-width layouts could therefore lack a reliable way to close tabs or access message, queued-message, and sidebar actions.

What changed

• Made tab close controls and touch-friendly message actions available on devices reporting a coarse pointer or no hover capability, regardless of viewport width.
• Extended queued-message action controls to those devices while preserving desktop hover behavior.
• Exposed sidebar actions on selected thread rows without hiding status indicators on unselected rows.
• Preserved image copying through the touch overflow menu.
• Kept upstream timeline naming and adapted icon sizing to the shared data-icon-root contract.

This is an app/shared-UI change with no server, protocol, CLI, or configuration changes.

How you verified

• pnpm exec turbo run typecheck --filter=@bb/app
• pnpm exec turbo run test --filter=@bb/app -- MessageActionBar ConversationMessageContent ThreadTimelineRows.actions docs-anatomy-manifest tab-pill theme.test QueuedMessagesList
• All 222 focused tests across 12 files passed.
• Coverage includes wide coarse-pointer and non-hover controls, queued actions, sidebar status preservation, and touch-menu image copying.
• git diff --check origin/main...HEAD passed.

AGENT GENERATED