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/plugins/base/plugin.go

@@ -0,0 +1,19 @@
+package base
+
+import (
+	"git.golem15.com/golem15/summercms/backpack"
+	"git.golem15.com/golem15/summercms/party"
+)
+
+// Plugin is the golem15.hello plugin.
+type Plugin struct{}
+
+func (p *Plugin) ID() string         { return "golem15.hello" }
+func (p *Plugin) Requires() []string { return nil }
+
+func (p *Plugin) Register(*backpack.App) error { return nil }
+func (p *Plugin) Boot(*backpack.App) error     { return nil }
+
+func init() {
+	party.Register(&Plugin{})
+}