feat: prefer stateful runtime for mcp content access

src/wf_sources_mcp/sdk/__init__.py

@@ -8,11 +8,12 @@ from .converters import (
     tool_to_discovered,
     workflow_output_schema_from_mcp_tool_schema,
 )
-from .protocols import BackendAdapter, ToolCallResult, ToolExecutor
+from .protocols import BackendAdapter, StatefulMcpRuntime, ToolCallResult, ToolExecutor
 
 __all__ = [
     "BackendAdapter",
     "McpSdkAdapter",
+    "StatefulMcpRuntime",
     "ToolCallResult",
     "ToolExecutor",
     "prompt_to_discovered",

src/wf_sources_mcp/sdk/protocols.py

@@ -99,8 +99,32 @@ class ToolExecutor(Protocol):
     ) -> ToolCallResult: ...
 
 
+class StatefulMcpRuntime(ToolExecutor, Protocol):
+    """Stateful execution/read boundary for configured MCP sources.
+
+    Implementations keep source session state across calls. Discovery/catalog
+    refresh may still use one-shot adapters by policy.
+    """
+
+    async def read_resource(
+        self,
+        connection: McpSourceConnection,
+        auth: AuthRecord | None,
+        uri: str,
+    ) -> dict[str, Any]: ...
+
+    async def get_prompt(
+        self,
+        connection: McpSourceConnection,
+        auth: AuthRecord | None,
+        prompt_name: str,
+        arguments: dict[str, str] | None = None,
+    ) -> dict[str, Any]: ...
+
+
 __all__ = [
     "BackendAdapter",
+    "StatefulMcpRuntime",
     "ToolCallResult",
     "ToolExecutor",
 ]