fix: offset scroll-to-bottom button when cancel bar visible

[simple-agent-manager]

Summary

• When the agent working indicator (cancel button) or connecting indicator is visible, the scroll-to-bottom button now shifts from -top-10 to -top-20 to avoid overlapping the status bar
• Added focus-visible outline ring to the scroll-to-bottom button for keyboard accessibility
• Uses transition-all for smooth position animation when status bar appears/disappears

Agent Preflight

• Change classification: ui-change
• Impact analysis: Single component change (ProjectMessageView.tsx), CSS positioning only, no data flow or API changes
• Assumption verification: Verified isPrompting and isConnecting are mutually exclusive states from the same hook state machine

Staging Verification

• Staging deployment green (run 23286473025)
• Live app verified via Playwright
• Existing workflows confirmed working (dashboard, projects, settings, navigation)
• API health endpoint healthy
• No console errors
• Note: The specific overlap fix requires an active agent session to visually verify; the positioning logic is a straightforward CSS conditional

Test plan

• Verify scroll-to-bottom button and cancel button do not overlap during active agent sessions
• Verify scroll button returns to normal position when agent stops (cancel bar disappears)
• Verify keyboard focus ring is visible on scroll-to-bottom button
• Test on mobile viewport widths

🤖 Generated with Claude Code

Co-Authored-By: Claude Opus 4.6 noreply@anthropic.com

[sonarqubecloud]

Quality Gate passed

Issues
0 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