Address review feedback: clear the scrub pill on every session-ending path

endSession(resync:) is the choke point for revertEditing, abortEditingForExternalPick,
and finishEditing's fallback paths, but only finishDragOrScrollSession cleared
rowScrubPreview. Escape-cancelling a scrub left the pill frozen on screen.

Author: superhighfives

Pika/Views/EditableColorValue.swift

@@ -521,6 +521,7 @@ struct EditableColorValue: View {
         isInvalid = false
         preEditColor = nil
         sessionOwner = nil
+        rowScrubPreview = nil
         // Only clear the own-write marker when we're about to resync anyway. A `resync: false`
         // commit (see `finishEditing`'s success path) deliberately keeps `values` as typed rather
         // than the freshly (and possibly lossily) decomposed colour — clearing this unconditionally