refactor: switch to basedpyright, remove pydantic-settings

- Replace pyright with basedpyright in devenv.nix (custom hook)
- Add basedpyright to devenv packages
- Fix all basedpyright warnings: add DiGraph[str] type args, annotate
  class attributes, narrow SyncResponse, handle unused call results,
  suppress unavoidable Any from yaml.safe_load and untyped blackforest
- Replace pydantic-settings[yaml] with direct pyyaml dependency
- Update CLAUDE.md to reflect basedpyright and dependency changes

bulkgen/cli.py

@@ -96,6 +96,6 @@ def graph() -> None:
             typer.echo(f"Stage {i} (targets): {', '.join(targets_in_gen)}")
 
         for node in gen:
-            predecessors = list(dep_graph.predecessors(node))
-            if predecessors:
-                typer.echo(f"  {node} <- {', '.join(predecessors)}")
+            preds: list[str] = list(dep_graph.predecessors(node))
+            if preds:
+                typer.echo(f"  {node} <- {', '.join(preds)}")