[Bug]: SingleChoiceComboBox uses the wrong border-radius during rebranding

[soulcramer]

Outcome

SingleChoiceComboBox applies the correct rebranded corner radius and matches the design-system shape tokens.

Problem

The rebranding shape tokens are not applied correctly in SingleChoiceComboBox; the component retains its old corner radius instead of the new one. Confirmed by a maintainer in #lbc-spark-android on 2026-06-25; a fix was planned in Spark but no PR or version was cited.

Context

The component likely hard-codes or falls back to a pre-rebrand shape value rather than consuming the current shape token.

• spark/src/main/kotlin/com/adevinta/spark/components/textfields/ComboBox.kt — shape/corner-radius application for SingleChoiceComboBox.

Scope

• Update SingleChoiceComboBox to consume the correct rebranded shape token for its corner radius.

Acceptance criteria

• SingleChoiceComboBox renders with the corner radius defined by the current rebranding shape tokens.
• A screenshot test covers the rebranded shape and fails if the radius regresses.

Evidence

• Slack: https://adevinta.enterprise.slack.com/archives/C04QQEU3Y2H/p1782401169474649 — Q.J., 2026-06-25
• spark/src/main/kotlin/com/adevinta/spark/components/textfields/ComboBox.kt — shape assignment for SingleChoiceComboBox.