[BUG]: Rename dialog loses focus when subagents spawn #14799

Description

When using /rename to rename a session while the agent is actively working, the rename dialog loses focus if subagents spawn. The user has to press Esc and run /rename again to continue typing.

The root cause is a reactive createEffect in packages/opencode/src/cli/cmd/tui/component/prompt/index.tsx that calls input.focus() on the main prompt whenever the visible prop re-evaluates. Since visible depends on session()?.parentID, permissions(), and questions() — all of which can change when subagents spawn via SSE events — the effect fires and steals focus from the rename dialog's textarea.

Steps to reproduce

1. Start a session and send a prompt that triggers subagent spawning
2. While the agent is working, type /rename to open the rename dialog
3. Observe that focus is stolen from the rename dialog when a subagent spawns
4. The rename input becomes unresponsive until you press Esc and /rename again

Operating System

macOS (not OS-specific, affects all platforms)