refactor(build): update Makefile to use example build directory and simplify serve target

Makefile

@@ -1,8 +1,8 @@
-.PHONY: all generate build build-debug build-opt test test-cover test-plugin test-browser lint fmt vet clean tidy deps verify serve help
+.PHONY: all generate build build-debug build-opt test test-cover test-plugin lint fmt vet clean tidy deps verify serve help
 
 MODULE := enclave
 BINARY := enclave.wasm
-BUILD_DIR := build
+BUILD_DIR := example
 
 all: generate build
 
@@ -10,15 +10,12 @@ generate:
 	@sqlc generate
 
 build:
-	@mkdir -p $(BUILD_DIR)
 	@GOOS=wasip1 GOARCH=wasm go build -o $(BUILD_DIR)/$(BINARY) .
 
 build-debug:
-	@mkdir -p $(BUILD_DIR)
 	@GOOS=wasip1 GOARCH=wasm go build -gcflags="all=-N -l" -o $(BUILD_DIR)/$(BINARY) .
 
 build-opt:
-	@mkdir -p $(BUILD_DIR)
 	@GOOS=wasip1 GOARCH=wasm go build -ldflags="-s -w" -o $(BUILD_DIR)/$(BINARY) .
 	@wasm-opt -Os $(BUILD_DIR)/$(BINARY) -o $(BUILD_DIR)/$(BINARY)
 
@@ -32,13 +29,9 @@ test-cover:
 test-plugin:
 	@extism call $(BUILD_DIR)/$(BINARY) generate --input '{"credential":"dGVzdA=="}' --wasi
 
-test-browser: build
-	@echo "Open http://localhost:8080/example/ in your browser"
-	@python3 -m http.server 8080
-
 serve: build
 	@echo "Open http://localhost:8080/example/ in your browser"
-	@python3 -m http.server 8080
+	@python3 -m http.server 8080 -d example
 
 lint:
 	@golangci-lint run ./...
@@ -51,7 +44,7 @@ vet:
 	@go vet ./...
 
 clean:
-	@rm -rf $(BUILD_DIR)
+	@rm -f $(BUILD_DIR)/$(BINARY)
 	@rm -f coverage.out coverage.html
 
 tidy:
@@ -78,8 +71,7 @@ help:
 	@echo "  test        - Run tests"
 	@echo "  test-cover  - Run tests with coverage"
 	@echo "  test-plugin - Test plugin with Extism CLI"
-	@echo "  test-browser- Build and serve for browser testing"
-	@echo "  serve       - Start local server for example/"
+	@echo "  serve       - Build and serve example/ for browser testing"
 	@echo "  lint        - Run golangci-lint"
 	@echo "  fmt         - Format code"
 	@echo "  vet         - Run go vet"