fix(mcp): accept transport field as alias for type (#3238) (#3243)

The official MCP configuration schema uses `transport` to specify the
transport mechanism (stdio/sse/http), but `McpServerConfig` only honored
`type` and defaulted to `stdio`. Remote MCP servers configured with just
`transport: sse` were therefore misidentified as stdio and failed with
"with stdio transport requires 'command' field".

Add a model validator that promotes `transport` to `type` when only
`transport` is provided, while keeping `type` authoritative when both
are set. This matches the MCP-spec field name without breaking existing
configurations.

Fixes #3238

backend/packages/harness/deerflow/config/extensions_config.py

@@ -5,7 +5,7 @@ import os
 from pathlib import Path
 from typing import Any, Literal
 
-from pydantic import BaseModel, ConfigDict, Field
+from pydantic import BaseModel, ConfigDict, Field, model_validator
 
 from deerflow.config.runtime_paths import existing_project_file
 
@@ -47,6 +47,24 @@ class McpServerConfig(BaseModel):
     description: str = Field(default="", description="Human-readable description of what this MCP server provides")
     model_config = ConfigDict(extra="allow")
 
+    @model_validator(mode="before")
+    @classmethod
+    def _accept_transport_alias(cls, data: Any) -> Any:
+        """Accept the MCP-spec ``transport`` field as an alias for ``type``.
+
+        The official MCP configuration schema uses ``transport`` to indicate
+        the transport mechanism (``stdio``/``sse``/``http``). Earlier versions
+        of this project only honored ``type``, which caused remote SSE/HTTP
+        servers configured with just ``transport`` to be incorrectly treated as
+        ``stdio`` (the default). This validator normalizes the two so either
+        spelling works, with ``type`` taking precedence when both are provided.
+        """
+        if isinstance(data, dict):
+            transport = data.get("transport")
+            if transport and not data.get("type"):
+                data = {**data, "type": transport}
+        return data
+
 
 class SkillStateConfig(BaseModel):
     """Configuration for a single skill's state."""