Fix e2e test build constraints to exclude WASM builds

Add !wasm constraint to e2e tests to prevent build errors when
compiling tests on host platform. Tests must run on host while
the main package compiles for WASM.

Author: claude

examples/calculator/calculator_e2e_test.go

@@ -1,4 +1,5 @@
-// +build e2e
+//go:build e2e && !wasm
+// +build e2e,!wasm
 
 package main