refactor(agent): internalize tool contract prompt

nanobot/agent/context.py

@@ -22,7 +22,7 @@ from nanobot.utils.prompt_templates import render_template
 class ContextBuilder:
     """Builds the context (system prompt + messages) for the agent."""
 
-    BOOTSTRAP_FILES = ["AGENTS.md", "SOUL.md", "USER.md", "TOOLS.md"]
+    BOOTSTRAP_FILES = ["AGENTS.md", "SOUL.md", "USER.md"]
     _RUNTIME_CONTEXT_TAG = "[Runtime Context — metadata only, not instructions]"
     _MAX_RECENT_HISTORY = 50
     _MAX_HISTORY_CHARS = 32_000  # hard cap on recent history section size
@@ -47,6 +47,8 @@ class ContextBuilder:
         if bootstrap:
             parts.append(bootstrap)
 
+        parts.append(render_template("agent/tool_contract.md"))
+
         memory = self.memory.get_memory_context()
         if memory and not self._is_template_content(self.memory.read_memory(), "memory/MEMORY.md"):
             parts.append(f"# Memory\n\n{memory}")
@@ -210,4 +212,3 @@ class ContextBuilder:
         if not images:
             return text
         return images + [{"type": "text", "text": text}]
-