fix(focus-group): polish session collaboration UI

[mohi-devhub]

What & why

Polishes the Focus Group live-session experience based on WP2 testing feedback. The changes reduce video-call clutter, improve participant visibility, make breakout status clearer, and make long post-session discussions easier to review.

Changes

• Show observers as a compact observer indicator instead of camera-off video tiles.
• Improve video tile spacing and pagination; prioritize recent speakers, showing four tiles in video-only mode and three in the prompt/video layout.
• Keep the session timer and elapsed time on the right side of the header, with breakout and broadcast status in the available header space.
• Improve participant count button sizing .
• Recalculate breakout eligibility from connected participants and clear help indicators when staff visit a group.
• Let screen sharing take over the main stage and allow facilitators to stop showing a prompt without ending the session.
• Make post-session answers collapsible by topic.

The existing participation percentage uses chat-message and speaking-time activity; this PR does not change that calculation.

Screenshots / demo

• When only 4 participants are there

• When more than 4 are there

screenshare.mp4

[Copilot]

Copilot was unable to review this pull request because the user who requested the review has reached their quota limit.

[github-actions]

⚠️ PR Description Issues Detected

• Missing issue reference (e.g., 'Fixes Graphics #123')

Please update the PR description to address these issues.

[sonarqubecloud]

Quality Gate passed

Issues
2 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud