implements dagger do

Signed-off-by: Richard Jones <richard@dagger.io>

tests/plan/hello-europa/main.cue

@@ -6,18 +6,18 @@ import (
 )
 
 dagger.#Plan & {
-	actions: {
-		image: dagger.#Pull & {
+	actions: test: {
+		_image: dagger.#Pull & {
 			source: "alpine:3.15.0@sha256:e7d88de73db3d3fd9b2d63aa7f447a10fd0220b7cbf39803c803f2af9ba256b3"
 		}
 
-		exec: dagger.#Exec & {
-			input: image.output
+		_exec: dagger.#Exec & {
+			input: _image.output
 			args: ["sh", "-c", "echo -n Hello Europa > /out.txt"]
 		}
 
-		verify: dagger.#ReadFile & {
-			input: exec.output
+		_verify: dagger.#ReadFile & {
+			input: _exec.output
 			path:  "/out.txt"
 		} & {
 			// assert result