fix(builder): boot drafts with the settings a new server really gets

The builder's boot test filled every blank password-like setting with a
throwaway value. A real deploy only fills x-generate fields, so a draft whose
server refuses to run with an empty join password passed the builder and CI,
and then shut down on its first real deploy.

The builder now boots drafts with boottest-payload -as-deployed: only
x-generate fields are filled, everything else exactly as the template's
defaults. A server that won't run with its own defaults fails the build, and
the model is told that empty settings stay empty, so the value must come from
a default or x-generate. CI's boot test is unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/gbrgames/build.go

@@ -240,7 +240,7 @@ func bootCheck(gamesDir, id, agentImage string, wantOutside bool) (problems, ver
 	// and the next deploy under the same name would trip over them
 	runCmd("docker", "rm", "-f", "boottest-"+id)
 	runCmd("docker", "volume", "rm", "-f", "boottest-"+id+"-data")
-	payloadCmd := exec.Command(self, "boottest-payload", "-games", gamesDir, id)
+	payloadCmd := exec.Command(self, "boottest-payload", "-as-deployed", "-games", gamesDir, id)
 	var stderr bytes.Buffer
 	payloadCmd.Stderr = &stderr
 	payload, err := payloadCmd.Output()
@@ -310,7 +310,9 @@ func bootFailure(output string) string {
 		lines = append(lines[:1], lines[len(lines)-59:]...)
 	}
 	return "booting your template with the node-agent (the real deploy code) failed: " + verdict +
-		". Find the cause in the server's output below and fix the template (startup command, settings, " +
+		". It was started with your defaults exactly as a new server gets them: settings left empty stay empty " +
+		"(only x-generate fields are filled), so a server that needs a value must get it from a default or " +
+		"x-generate. Find the cause in the server's output below and fix the template (startup command, settings, " +
 		"ready pattern, memory):\n" + strings.Join(lines, "\n")
 }