[codex] Fix agent visual fullscreen styles

[rogerchappel]

Summary

• Restore fullscreen Agent Mode visual behavior after the tray visual consistency merge.
• Prevent non-orbital visual styles from being covered by the generic speaker/core layer.
• Mark Agent Mode overlay controls as explicit buttons so mobile taps do not behave like composer submits.

Why

Post-merge testing showed fullscreen Agent Mode collapsed into the compact composer area on mobile, and the new visual styles rendered as a speaker/core picture instead of their actual style. This PR contains only that feedback fix on top of current main.

Verification

• pnpm typecheck
• pnpm test src/lib/agent-visual-settings.test.ts 'src/app/api/companies/[id]/route.test.ts'
• pnpm lint:check (existing warnings only)
• git diff --check origin/main...HEAD
• visual regression smoke for non-orbital style rendering and Orbital immersive classes
• push hook: pnpm typecheck and pnpm build