refactor: remove legacy assistant compatibility

backend/services/tool_policy.py

@@ -1,9 +1,4 @@
-"""Runtime behavior shared by HTTP, MCP, and client tools.
-
-The stored definitions are intentionally plain dictionaries.  Keeping policy
-normalization here gives old definitions stable defaults without spreading
-fallback rules across PromptBrain, WorkflowBrain, and the pipeline.
-"""
+"""Runtime behavior shared by HTTP, MCP, and client tools."""
 
 from __future__ import annotations
 
@@ -33,18 +28,14 @@ class ToolRuntimePolicy:
 
 
 def policy_for_tool(tool: RuntimeTool) -> ToolRuntimePolicy:
-    """Read policy with backwards-compatible defaults per tool kind."""
-    config = (tool.definition or {}).get("config") or {}
-    default_mode = "async" if tool.type == "client" else "immediate"
-    mode = str(config.get("execution_mode") or default_mode)
-    if mode not in {"immediate", "async"}:
-        mode = default_mode
-    response_wait_mode = str(config.get("response_wait_mode") or "timeout")
-    if response_wait_mode not in {"timeout", "session"}:
-        response_wait_mode = "timeout"
+    """Read the validated policy stored on a current tool resource."""
+    config = tool.definition["config"]
+    is_client = tool.type == "client"
     return ToolRuntimePolicy(
-        allow_interruptions=bool(config.get("allow_interruptions", True)),
-        execution_mode=mode,
-        wait_for_response=bool(config.get("wait_for_response", True)),
-        response_wait_mode=response_wait_mode,
+        allow_interruptions=bool(config["allow_interruptions"]),
+        execution_mode=str(config["execution_mode"]),
+        wait_for_response=(bool(config["wait_for_response"]) if is_client else True),
+        response_wait_mode=(
+            str(config["response_wait_mode"]) if is_client else "timeout"
+        ),
     )