scripts(typing[mcp_swap]): cast claude project node return to fix CI mypy

CI runs ``uv run mypy .`` against the whole tree, picking up
``scripts/mcp_swap.py``. ``_claude_project_node`` returned a value
sourced from ``Any`` JSON, and the runtime isinstance guard didn't
propagate to the return site, tripping ``no-any-return``. Cast to the
documented narrowed shape — the existing guards already establish the
invariant.

Author: tony

scripts/mcp_swap.py

@@ -286,7 +286,11 @@ def _claude_project_node(
     if node is None and create:
         node = {"allowedTools": [], "mcpContextUris": [], "mcpServers": {}, "env": {}}
         projects[key] = node
-    return node
+    # ``projects`` came from an ``Any``-typed JSON tree, so ``node`` lands as
+    # ``Any`` and the isinstance guard above doesn't propagate to the return
+    # site. Cast to the documented narrowed type — the runtime guards
+    # establish the invariant.
+    return t.cast("dict[str, t.Any] | None", node)
 
 
 def get_server(