feat(ioscompanion): embed and extract the runner test bundle

internal/driver/ioscompanion/runnerassets/embed_stub.go

@@ -0,0 +1,10 @@
+//go:build !withcompanion
+
+package runnerassets
+
+var embeddedArchive []byte
+
+// IsPlaceholder reports whether the binary was built without the real runner
+// archive embedded. Build with `make sanderling` (which passes
+// -tags withcompanion) to embed the real runner test bundle.
+func IsPlaceholder() bool { return true }