Settle retained final answer geometry

[VolkerChristian]

Summary

• establish each retained nested card's real width before measuring wrapped rich-text height
• synchronously settle child and outer turn-card layouts in dependency order
• cover partial retained hydration, nesting, and width changes with a regression test

Verification

• codex-ui builds successfully
• codexui-conversation-cards-test passes
• retained Codex App-Server Analyses thread was reloaded and visually checked under Xvfb; the complete final answer and both final list items remain inside the card