harden agent builder render guidance

tests/test_builder_prompt.py

@@ -0,0 +1,19 @@
+from __future__ import annotations
+
+import unittest
+
+from agent_builder.builder import SYSTEM_PROMPT
+
+
+class BuilderPromptTests(unittest.TestCase):
+    def test_prompt_requires_resource_mirror_for_heavy_agents(self) -> None:
+        self.assertIn("declare resources in BOTH places", SYSTEM_PROMPT)
+        self.assertIn("resources = Resources", SYSTEM_PROMPT)
+        self.assertIn("runtime:", SYSTEM_PROMPT)
+        self.assertIn("max_runtime_seconds", SYSTEM_PROMPT)
+
+    def test_prompt_requires_live_schema_check_and_manim_contract(self) -> None:
+        self.assertIn("live_skills[].input_schema", SYSTEM_PROMPT)
+        self.assertIn("class GeneratedDeck(Slide)", SYSTEM_PROMPT)
+        self.assertIn("manim-slides render --CE -ql", SYSTEM_PROMPT)
+        self.assertIn("render: bool = False", SYSTEM_PROMPT)