build: add Makefile with WASM build target and size check

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

.gitignore

@@ -0,0 +1 @@
+dist/

Makefile

@@ -0,0 +1,22 @@
+.PHONY: wasm test clean
+
+WASM_OUT := dist/go-html.wasm
+
+test:
+	go test ./...
+
+wasm: $(WASM_OUT)
+
+$(WASM_OUT):
+	@mkdir -p dist
+	GOOS=js GOARCH=wasm go build -ldflags="-s -w" -o $(WASM_OUT) ./cmd/wasm/
+	@ls -lh $(WASM_OUT)
+	@SIZE=$$(stat -c%s "$(WASM_OUT)" 2>/dev/null || stat -f%z "$(WASM_OUT)"); \
+	if [ "$$SIZE" -gt 2097152 ]; then \
+		echo "WARNING: WASM binary exceeds 2MB target ($${SIZE} bytes)"; \
+	else \
+		echo "OK: WASM binary within 2MB target ($${SIZE} bytes)"; \
+	fi
+
+clean:
+	rm -rf dist/