feat: build mcp server from workflow config

docs/current_roadmap.md

@@ -181,6 +181,10 @@ implementation state.
     `kind: "mcp"` entries with stdio/http transport, auth reference, metadata,
     enabled flag, and `locked` / `seed` ownership policy. Runtime composition
     from these entries is the next slice.
+    Runtime bridge complete: neutral `kind: "mcp"` source entries can now build
+    the MCP-backed `WorkflowServer`. `--mcp-config` remains supported as a
+    legacy compatibility path while new configs should prefer
+    `server.sources[]`.
   - Transport package boundary cleanup follows the config migration. The current
     `wf-rpc-server --mcp-config` hookup proves the product path but makes
     `wf_transport_rpc_http.cli` import `wf_mcp.broker`, tripping the existing

docs/superpowers/specs/2026-06-03-long-lived-workflow-api-boundary.md

@@ -118,6 +118,10 @@ Model slice complete when `wf_config.server.sources[]` accepts `kind: "mcp"`
 entries. The next slice converts those neutral source entries into MCP
 broker runtime connections and server composition.
 
+Runtime bridge complete when `wf-rpc-server --config <path>` can compose an
+MCP-backed server from neutral `server.sources[]` entries. `--mcp-config`
+remains a compatibility alias until existing users migrate.
+
 First slice should not include:
 
 - live upstream MCP source management

docs/wf_cli.md

@@ -21,6 +21,29 @@ Start a local/static JSON-RPC workflow server:
 wf-rpc-server --store-root .wf_store --host 127.0.0.1 --port 8765
 ```
 
+Prefer neutral workflow config for new MCP-backed servers:
+
+```json
+{
+  "version": 1,
+  "server": {
+    "store": {"kind": "filesystem", "root": ".wf_store"},
+    "transports": [{"kind": "rpc_http", "host": "127.0.0.1", "port": 8765}],
+    "sources": [
+      {
+        "kind": "mcp",
+        "id": "everything.default",
+        "provider": "everything",
+        "account": "default",
+        "transport": {"kind": "stdio", "command": "uvx", "args": ["mcp-server-everything"]}
+      }
+    ]
+  }
+}
+```
+
+`--mcp-config` is still accepted for legacy broker config files.
+
 Start a JSON-RPC server backed by MCP broker config and MCP-capable sources:
 
 ```bash