test: mirror testkit's (prefix, router) convention in the fake registry

Verified register() against the real host loader + PluginRegistry: the module
imports as a package (relative imports resolve), the factory returns None when
disabled and a 17-tool stdio entry when enabled, and prefix="" mounts without
tripping the server-side _prefix_conforms check.

The real registry stores {"router", "prefix"} and a resolved Path; both
host-free fakes simplify, so follow the sanctioned one in
graph/plugins/testkit.py rather than inventing a third shape.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01U69poCC3qyCbTnaJmRzBvi

Author: Josh Mabry

tests/conftest.py

@@ -50,7 +50,10 @@ def register_skill_dir(self, path) -> None:
         self.skill_dirs.append(path)
 
     def register_router(self, router, prefix=None) -> None:
-        self.routers.append((router, prefix))
+        # (prefix, router) mirrors graph/plugins/testkit.py's convention. The real
+        # registry stores {"router", "prefix"} and resolves the effective prefix;
+        # the host-free fakes both simplify, so follow the sanctioned one.
+        self.routers.append((prefix, router))
 
     def register_tool(self, tool) -> None:
         self.tools.append(tool)

tests/test_register.py

@@ -33,10 +33,9 @@ def test_the_skill_dir_exists(registered):
 def test_registers_the_test_route_at_the_convention_path(registered):
     """`/api/config/test-<section>` is a fixed URL; prefix="" is the sanctioned
     escape hatch (the core chat-surface wirer uses the same one)."""
-    _, prefix = registered.routers[0]
+    prefix, router = registered.routers[0]
     assert prefix == ""
-    paths = [r.path for r in registered.routers[0][0].routes]
-    assert "/api/config/test-cua" in paths
+    assert "/api/config/test-cua" in [r.path for r in router.routes]
 
 
 def test_registers_no_tools(registered):