Fixes#17954.
## Why
When a manual shell command like `!sleep 10` is running, submitting
plain text such as `hi` currently sends that text as a steer for the
active shell turn. User shell turns are not steerable like model turns,
so the TUI can remain stuck in `Working` after the shell command
finishes.
## What Changed
- Detect when the only active work is one or more
`ExecCommandSource::UserShell` commands.
- Queue plain submitted input in that state so it drains after the shell
command and shell turn complete.
- Preserve `!cmd` submissions during running work so explicit shell
commands keep their existing behavior.
- Add regression coverage for the `!sleep 10` plus `hi` flow in
`chatwidget::tests::exec_flow::user_message_during_user_shell_command_is_queued_not_steered`.
## Verification
- Manually confirmed hang before the fix and no hang after the fix
## Why
Users have asked to queue follow-up slash commands while a task is
running, including in #14081, #14588, #14286, and #13779. The previous
TUI behavior validated slash commands immediately, so commands that are
only meaningful once the current turn is idle could not be queued
consistently.
The queue should preserve what the user typed and defer command parsing
until the item is actually dispatched. This also gives `/fast`, `/review
...`, `/rename ...`, `/model`, `/permissions`, and similar slash
workflows the same FIFO behavior as plain queued prompts.
## What Changed
- Added a queued-input action enum so queued items can be dispatched as
plain prompts, slash commands, or user shell commands.
- Changed `Tab` queueing to accept slash-led prompts without validating
them up front, then parse and dispatch them when dequeued.
- Added `!` shell-command queueing for `Tab` while a task is running,
while preserving existing `Enter` behavior for immediate shell
execution.
- Moved queued slash dispatch through shared slash-command parsing so
inline commands, unavailable commands, unknown commands, and local
config commands report at dequeue time.
- Continued queue draining after local-only actions and after slash menu
cancellation or selection when no task is running.
- Preserved slash-popup completion behavior so `/mo<Tab>` completes to
`/model ` instead of queueing the prefix.
- Updated pending-input preview snapshots to show queued follow-up
inputs.
## Verification
I did a bunch of manual validation (and found and fixed a few bugs along
the way).
Problem: `chatwidget/tests.rs` had grown into a single oversized test
blob that was hard to maintain and exceeded the repo's blob size limit.
Solution: split the chatwidget tests into topical modules with a thin
root `tests.rs`, shared helper utilities, preserved snapshot naming, and
hermetic test config so the refactor stays stable and passes the
`codex-tui` test suite.
Michael Bolin