Delete evaluator.py shim: all imports go directly to bootstrapped sx_ref.py

EvalError moved to types.py. All 27 files updated to import eval_expr,
trampoline, call_lambda, etc. directly from shared.sx.ref.sx_ref instead
of through the evaluator.py indirection layer. 320/320 spec tests pass.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

shared/sx/ref/run_py_sx.py

@@ -38,7 +38,7 @@ def load_py_sx(evaluator_env: dict) -> dict:
     exprs = parse_all(source)
 
     # Import the evaluator
-    from shared.sx.evaluator import evaluate, make_env
+    from shared.sx.ref.sx_ref import evaluate, make_env
 
     env = make_env()
     for expr in exprs:
@@ -60,7 +60,7 @@ def extract_defines(source: str) -> list[tuple[str, list]]:
 
 
 def main():
-    from shared.sx.evaluator import evaluate
+    from shared.sx.ref.sx_ref import evaluate
 
     # Load py.sx into evaluator
     env = load_py_sx({})