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

cmd/summer/main.go

@@ -85,6 +85,10 @@ files: every build rewrites them.`,
 				if line == "" {
 					continue
 				}
+				if rest, ok := strings.CutPrefix(line, "warning: "); ok {
+					out.Warning(strings.TrimSuffix(rest, "\n"))
+					continue
+				}
 				if rest, ok := strings.CutPrefix(line, "built "); ok && err == nil {
 					out.Success("Built bin/" + strings.TrimSuffix(rest, "\n"))
 					continue