refactor: isolate rpc server config composition

src/wf_server/config.py

@@ -0,0 +1,57 @@
+from __future__ import annotations
+
+from pathlib import Path
+
+from wf_config import FilesystemStoreConfig, WorkflowConfigFile
+
+from .context import WorkflowServer, build_local_static_workflow_server
+
+
+def _has_mcp_sources(config: WorkflowConfigFile) -> bool:
+    return any(getattr(source, "kind", None) == "mcp" for source in config.server.sources)
+
+
+def _build_mcp_workflow_server_from_workflow_config(
+    config: WorkflowConfigFile,
+) -> WorkflowServer:
+    """Build an MCP-backed server from neutral config.
+
+    This import is intentionally isolated here: transport packages should not
+    import MCP modules, while this server composition boundary is allowed to
+    select source-provider implementations by source kind.
+    """
+    from wf_mcp.broker import build_workflow_server_from_workflow_config
+
+    return build_workflow_server_from_workflow_config(config)
+
+
+def _build_mcp_workflow_server_from_legacy_config(path: Path) -> WorkflowServer:
+    """Build an MCP-backed server from legacy broker config."""
+    from wf_mcp.broker import build_workflow_server_from_config, load_broker_config
+
+    return build_workflow_server_from_config(load_broker_config(path))
+
+
+def build_workflow_server_from_workflow_config(
+    config: WorkflowConfigFile,
+) -> WorkflowServer:
+    """Build a WorkflowServer from neutral workflow config.
+
+    Local/static configs use built-in sources. Configs with ``kind: "mcp"``
+    sources delegate to the MCP provider adapter.
+    """
+    if _has_mcp_sources(config):
+        return _build_mcp_workflow_server_from_workflow_config(config)
+    store = config.server.store
+    if not isinstance(store, FilesystemStoreConfig):
+        raise ValueError("wf-rpc-server currently requires filesystem store")
+    return build_local_static_workflow_server(store.root)
+
+
+def build_workflow_server_from_legacy_mcp_config(path: str | Path) -> WorkflowServer:
+    """Build a WorkflowServer from legacy wf_mcp.config.json.
+
+    Prefer neutral ``wf_config`` for new setups. This compatibility hook keeps the
+    transport CLI free of direct MCP imports while existing users migrate.
+    """
+    return _build_mcp_workflow_server_from_legacy_config(Path(path))