Clarify Agentbox names and invariants

Co-authored-by: codegirl007 <codegirl-007@users.noreply.github.com>

agentbox/internal/agent/deterministic.go

@@ -76,6 +76,8 @@ func greenCentroidX(screenshot []byte) (float64, error) {
 	for y := bounds.Min.Y; y < bounds.Max.Y; y++ {
 		for x := bounds.Min.X; x < bounds.Max.X; x++ {
 			red, green, blue, _ := renderedImage.At(x, y).RGBA()
+			// Match the mover's #00ff66 square. Requiring 1,000 matching pixels
+			// prevents a small green UI detail from passing verification.
 			if green > 0xc000 && red < 0x4000 && blue < 0x8000 {
 				xCoordinateSum += uint64(x)
 				greenPixelCount++

agentbox/internal/agent/openai_protocol.go

@@ -87,12 +87,14 @@ func modelPrompt(task string, history []Step, observation Observation) (string,
 		return "", err
 	}
 	return "You control an interactive Linux application from screenshots. " +
-		"Choose exactly one safe input action, or mark done when the task is complete. " +
+		"Choose exactly one allowed input action, or mark done when the task is complete. " +
 		"Use logical key names such as RIGHT, ENTER, or ESCAPE. Keep waits under 5000 ms.\n" +
 		string(data), nil
 }
 
 func decisionSchema() map[string]any {
+	// Strict structured output requires every action property to be present,
+	// even when a particular action ignores most of them.
 	actionProperties := map[string]any{
 		"type": map[string]any{
 			"type": "string",