Add manual opener tool calls to Assistant model and API

- Introduced `manual_opener_tool_calls` field in the Assistant model to support custom tool calls.
- Updated AssistantBase and AssistantUpdate schemas to include the new field.
- Implemented normalization and migration logic for handling manual opener tool calls in the API.
- Enhanced runtime metadata to include manual opener tool calls in responses.
- Updated tests to validate the new functionality and ensure proper handling of tool calls.
- Refactored tool ID normalization to support legacy tool names for backward compatibility.

engine/core/session.py

@@ -66,6 +66,7 @@ class Session:
         "firstTurnMode",
         "greeting",
         "generatedOpenerEnabled",
+        "manualOpenerToolCalls",
         "systemPrompt",
         "output",
         "bargeIn",
@@ -973,6 +974,7 @@ class Session:
         passthrough_keys = {
             "firstTurnMode",
             "generatedOpenerEnabled",
+            "manualOpenerToolCalls",
             "output",
             "bargeIn",
             "knowledgeBaseId",