fix(tui): preserve first prompt in fresh sessions

[jlongster]

Summary

• mark sessions created from the Home prompt as fresh
• skip the initial history refresh for fresh sessions so admitted input events remain visible
• retain full history refreshes when sessions are reopened normally
• add regression coverage for preserving an admitted prompt through promotion

Testing

• bun test test/cli/tui/data.test.tsx --timeout 30000
• bun run typecheck in packages/tui
• OpenCode Drive: 100 fresh sessions, 100 prompts visible, 100 responses visible, 0 reproductions