wip: partial implementation salvaged from interrupted workflow run

Untrusted draft — no build/test had run yet. Review before building on it.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

ErsatzTV.Application/ProgramSchedules/ProgramScheduleItemsWithDurationViewModel.cs

@@ -0,0 +1,19 @@
+namespace ErsatzTV.Application.ProgramSchedules;
+
+/// <summary>
+///     The items of a schedule together with computed runtime estimates. Each item carries its own
+///     <see cref="ProgramScheduleItemViewModel.DurationEstimate" /> (nullable — see that property for
+///     the per-mode semantics), and <see cref="TotalDurationEstimate" /> is the sum of the items that
+///     could be estimated.
+/// </summary>
+/// <param name="Items">The schedule items, each with a nullable <c>DurationEstimate</c>.</param>
+/// <param name="TotalDurationEstimate">
+///     The sum of every non-null per-item estimate, i.e. a rough runtime for a single pass through the
+///     estimable items. <c>null</c> when no item in the schedule could be estimated (for example a
+///     schedule made up entirely of Flood/Duration items, or of collection types that are not
+///     aggregated). Because unbounded items contribute nothing, this is a lower bound, never an exact
+///     schedule length.
+/// </param>
+public record ProgramScheduleItemsWithDurationViewModel(
+    List<ProgramScheduleItemViewModel> Items,
+    TimeSpan? TotalDurationEstimate);