- Add PopLastUserMessage() on *App: walks the current tree branch back to
the parent of the most recent user message, syncs the in-memory store,
and returns the prompt + image parts for resubmission.
- Register /retry (alias /rt) and wire handleRetryCommand which rebuilds
the visible ScrollList from the truncated branch before resubmitting
via Run/RunWithFiles. Mirrors SubmitMsg display path (badges, pending
prints, stateWorking transition).
- Recovers from transient provider errors (overloaded, timeout) without
duplicating the user message in context — the failed turn's entries
become orphaned off-branch rather than being re-sent to the LLM.
- Update help text, AppController interface, and stub controller.
- Add unit tests covering busy/closed/no-session guards, the happy-path
truncation, and the empty-branch error case.
Ed Zynda
6100e8b3a8