StepperCommandDialog has no footer Cancel action

[woksin]

Problem / motivation

This issue promotes a previously recorded upstream item from a production Cratis consumer. The complete evidence, proposed seam and limits follow.

Status: Open upstream improvement · filing in progress 2026-08-10
Product: Components — StepperCommandDialog
Class: Missing dialog action seam

Gap and Ada cost

The stepper footer exposes Previous/Next/Submit but no Cancel. Cancellation is available only through the dialog X,
which is less discoverable, may not match the product's dialog action contract and gives consumers no supported way
to place Cancel beside the other actions without replacing the footer and its command wiring.

Requested seam

Add an opt-in localized Cancel footer action using the dialog's normal hide/result path, with placement consistent
across first, middle and final steps. Keep the existing X behavior.

Honest limits

This is source/API evidence; Ada has not measured a user failure caused by the missing footer action.

[woksin]

Fixed in #129, shipped in v2.8.0 (merge b02dc789).

StepperCommandDialog now takes an opt-in showCancel, with cancelLabel for the wording. It sits in the footer alongside Previous/Next/Submit, and takes the same cancel arm the header X and Escape already took, so a consumer's onCancel sees one behavior regardless of how the dialog was dismissed.

Two things were found while reviewing it that were not part of the original request but shipped in the same change, because the new button is what makes them reachable:

• The dialog raised its busy flag only after awaiting a consumer's onBeforeExecute transform. With an async transform that left a window in which the command was already committed to running while Cancel was still live — the operator cancelled, the dialog closed reporting cancellation, and the write landed anyway. The busy flag is now raised as the first statement of the submit path.
• The header close and Escape were not withdrawn while a command was running, even though the footer Cancel was. All three dismissal routes are now withdrawn together.

Both are documented in Documentation/StepperCommandDialog/index.md, along with the two new props — which the first pass shipped undocumented while the surrounding prose still claimed cancel is always available via the header X.

Independent code and security review of the original implementation is recorded on #129, including a spec that could not fail and has been fixed.