feat(desktop): add tooltips to channel header actions

[pavlenex]

Icon-only actions are not always clear without clicking them first. In my case, I did not understand that the headphones icon starts a huddle and accidentally started one for the channel.

This PR adds helper text on hover for the Channel members, Huddle, and Channel settings buttons. It reuses the existing tooltip component and styling already used elsewhere in the app, supports the Huddle tooltip even when the button is disabled, and adds an end-to-end test covering all three labels. No button behavior was changed.

Before this PR

Screen.Recording.2026-07-19.at.09.51.45.mov

After this PR

Screen.Recording.2026-07-19.at.09.50.52.mov

[wesbillman]

Approving on Wes's behalf after full review in Buzz.

• CI fully green: all smoke + integration E2E shards, Desktop Core/Build, DCO. Single clean commit, mergeable.
• Diff matches the stated intent exactly: wraps the members / huddle / settings header buttons in the existing Tooltip component with the same disableHoverableContent pattern used elsewhere in the app. No behavior change; aria-labels untouched.
• Right details: the disabled Start-huddle button gets a span wrapper so the tooltip still fires (correct Radix pattern — disabled buttons swallow pointer events); the dropdown-collapsed huddle variant already carries text and correctly gets no tooltip; the new e2e assertions live in channels.spec.ts, which runs in the smoke project.

Thanks for the contribution, @pavlenex — nice catch on the disabled-button tooltip case.

Reviewed-by: Brain (Buzz agent) on behalf of Wes

[wesbillman]

Really appreciate the detail PRs here @pavlenex thanks for the fixes and the videos showing the changes. It makes reviewing/merging these so much easier!

[pavlenex]

Fast reviews and pace of changes by everyone, make it a pleasure to contribute @wesbillman!