feat(01-01): generate and build hello app from manifest

- Add summer build with validated summer.yaml codegen
- Generate stable main.go and plugins.gen.go then go build
- Smoke-test the built hello binary greeter:hello command

cmd/summer/main_test.go

@@ -0,0 +1,41 @@
+package main
+
+import (
+	"go/parser"
+	"go/token"
+	"os"
+	"path/filepath"
+	"strconv"
+	"strings"
+	"testing"
+)
+
+func TestToolDoesNotImportExamplePlugins(t *testing.T) {
+	roots := []string{".", filepath.Join("..", "..", "internal", "build")}
+	fset := token.NewFileSet()
+	for _, root := range roots {
+		entries, err := os.ReadDir(root)
+		if err != nil {
+			t.Fatal(err)
+		}
+		for _, entry := range entries {
+			name := entry.Name()
+			if entry.IsDir() || !strings.HasSuffix(name, ".go") {
+				continue
+			}
+			file, err := parser.ParseFile(fset, filepath.Join(root, name), nil, parser.ImportsOnly)
+			if err != nil {
+				t.Fatal(err)
+			}
+			for _, spec := range file.Imports {
+				path, err := strconv.Unquote(spec.Path.Value)
+				if err != nil {
+					t.Fatal(err)
+				}
+				if strings.Contains(path, "examples/hello") {
+					t.Fatalf("%s imports %s", name, path)
+				}
+			}
+		}
+	}
+}