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/pages.py

@@ -127,7 +127,7 @@ def get_page_helpers(service: str) -> dict[str, Any]:
 def load_page_file(filepath: str, service_name: str) -> list[PageDef]:
     """Parse an .sx file, evaluate it, and register any PageDef values."""
     from .parser import parse_all
-    from .evaluator import _eval as _raw_eval, _trampoline
+    from .ref.sx_ref import eval_expr as _raw_eval, trampoline as _trampoline
     _eval = lambda expr, env: _trampoline(_raw_eval(expr, env))
     from .jinja_bridge import get_component_env