feat(build): bake plugin metadata and the framework version into plugins.gen.go

- party.Info, party.Installed, party.Describe (additive; Plugin and Activate unchanged)
- summer build resolves plugin dirs with one go list, reads plugin.yaml, versions per D-07 (module version, git describe without --dirty, none for in-app plugins)
- build.EffectiveFramework: newest tag of a locally replaced or used framework checkout, else the go.mod require
- generated main calls party.Describe(app, PluginInfo, FrameworkVersion) before Activate; metadata failures warn and fall back to IDs
- summer new goldens and examples/hello regenerated

examples/hello/main.go

@@ -34,6 +34,9 @@ func run(args []string, out io.Writer) int {
 		return bonfire.Fail(os.Stderr, "hello", err, g)
 	}
 	app := backpack.New(cfg)
+	if err := party.Describe(app, PluginInfo, FrameworkVersion); err != nil {
+		return bonfire.Fail(os.Stderr, "hello", err, g)
+	}
 	plugins, err := party.Activate(app, PluginIDs)
 	if err != nil {
 		return bonfire.Fail(os.Stderr, "hello", err, g)