fix(runner): mark nil/empty hierarchy as transitional

A failed or empty sidecar hierarchy fetch was pushed straight to the
verifier, letting spec extractors crash with "Cannot read property 'map'
of undefined" when findAll returned null. Treat that case like a
transitional capture: skip the verifier push, still record the step, and
keep the loop progressing.

internal/runner/runner.go

@@ -139,6 +139,14 @@ func Run(ctx context.Context, options Options) (Summary, error) {
 		if tree != nil {
 			treeSize = len(tree.Elements)
 		}
+		// A nil or empty tree means the sidecar's hierarchy fetch failed or
+		// returned nothing (e.g. transient device-side timeout). Pushing it
+		// would let spec extractors call findAll() and chain .map() on a null
+		// result; treat it like a transitional capture so the verifier is
+		// skipped, the step is still recorded, and the loop progresses.
+		if treeSize == 0 {
+			transitional = true
+		}
 		lastLogTime = stepStart
 
 		screen := ""