## Why
Session transitions need stack headroom to rebuild configuration and the chat widget. Tokio stores task outputs inline even when it boxes the task future, so returning a large `Config` adds stack pressure during task allocation.
## What changed
Box the configuration build result inside the runtime worker and unbox it after joining. Box the `App::run` future to keep the large event loop out of enclosing startup futures.
## Testing
Extend the production-stack TUI integration test to enter `/side`, verify the process remains running, and return to the saved conversation with Ctrl+C.
GitOrigin-RevId: 44975300bb837bf3645ff762cf7bcdc44a277f41
## Why
Session transitions need stack headroom for embedded-server initialization and configuration loading. Running them inside event dispatch risks exhausting the TUI thread's stack.
## What changed
- Queue `/resume` and valid `/cd` requests for processing after event dispatch returns.
- Reject additional `/cd` requests while one is pending, and recheck the source session, working directory, idle state, and remote-environment restrictions before applying it.
## Testing
Add a Unix PTY regression test that exercises `/resume`, worktree conversation forks, `/cd`, and new worktree conversations through the real TUI event loop. Update the directory-change test to verify that dispatch queues the request without immediately changing configuration.
GitOrigin-RevId: 4950921931dfaba9e55e6bb04f98f7ba64b72122
Eric Traut