fix(ui,app): allow context tooltip on touch and add mobile context tab

[fydiog]

Fixes #10443

This PR addresses the issue where mobile/touch devices cannot access context details because our Tooltip captures and blocks pointer-down events (preventing Kobalte from opening on tap), and because the simplified mobile tab bar does not include a Context tab.

Changes:

• packages/ui/src/components/tooltip.tsx: Skip the arm() call on touch pointer events so tapping a tooltip trigger opens the tooltip instead of suppressing it.
• packages/app/src/pages/session.tsx: Add a 'context' option to the mobile tab bar, adjust tab widths to 1/3, and render when that tab is active.

Verified on local dev build with simulated touch viewport.

[github-actions]

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