[Bug] Agent context lost when switching to fullscreen mode in TUI

Bug Description
Start claude with --agent foo

Run /tui fullscreen

Switches to fullscreen and loses the agent.

Environment Info

• Platform: darwin
• Terminal: iTerm.app
• Version: 2.1.119
• Feedback ID: 8db0eb15-ae33-45f6-890c-6f47442c3569

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/joelc/.local/share/claude/versions/2.1.119 (expected in multi-process scenarios)\n    at mH6 (/$bunfs/root/src/entrypoints/cli.js:2736:2177)\n    at E$8 (/$bunfs/root/src/entrypoints/cli.js:2736:1257)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-04-24T00:54:31.234Z"}]