CngxMatTabRejectionContentContext

Context passed to the *cngxMatTabRejectionContent template. Drives the SR-descriptor content rendered inside the <span class="cngx-sr-only"> decoration that [cngxMatTabs] appends to a Material tab button when its bound commitAction rejects a tab change. The surrounding span (with its cngx-sr-only class, its stable id, and the aria-describedby wiring on the button) stays library-owned - the slot only customises the descriptor text or markup so consumers can swap the rejection phrasing (branded prefixes, retry CTAs, localised templates) without fighting the AT contract.

failedHandleId is the stable id of the rejected handle (the same id the descriptor span uses as its ${id}-rejected DOM id); originLabel is the label the rollback returned to (when the presenter exposes an originIndexDuringCommit and that index resolves to a handle with a non-empty label) - undefined when no labelled rollback origin is resolvable; fallbackText is the built-in i18n phrase the imperative fallback path would write verbatim (typically commitRolledBackTo(originLabel) when the origin is resolvable, commitFailedRetry otherwise).

Re-instantiation warning. The decoration projector destroys the embedded view and creates a fresh one on every descriptorText re-emission - typical when the rollback origin label resolves later than the failed-handle id (e.g. presenter.tabs() re-emits mid-rejection and the origin label flows in on the second tick). The slot template runs to the end of its lifecycle each time; consumers wiring expensive subtrees (e.g. an embedded chart, a complex form) should treat this as a destroy + remount cycle and lift heavy state into a sibling *ngTemplateOutlet-friendly structure outside the slot. Cheap text + simple markup (the intended use) sees no observable difference.