feat(01-01): boot hello app and dispatch greeter:hello

- Add party plugin registry with Register-before-Boot activation
- Add backpack, compass, bonfire, and pact capability interfaces
- Add examples/hello with two compiled plugin modules

examples/hello/hello_test.go

@@ -0,0 +1,17 @@
+package main
+
+import (
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestGreeterHelloPrintsAppName(t *testing.T) {
+	var buf bytes.Buffer
+	if err := run([]string{"greeter:hello"}, &buf); err != nil {
+		t.Fatalf("greeter:hello: %v", err)
+	}
+	if got := strings.TrimSpace(buf.String()); got != "hello-app" {
+		t.Fatalf("output = %q, want %q", got, "hello-app")
+	}
+}