experimental: remove Unimplemented server stub from generated output

The codegen was emitting an `Unimplemented` struct with stub methods
(returning StatusNotImplemented) into every generated server file. This
adds noise to generated output and is better left to consumers to
implement if desired. Remove it from all 7 framework interface templates
(chi, echo, echo-v4, gin, fiber, gorilla, iris) and regenerate examples.

The stdhttp template already did not include this stub.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: mromaszewicz

experimental/examples/petstore-expanded/chi/server/server.gen.go

@@ -11,14 +11,3 @@ type ServerInterface interface {
 	{{ .GoOperationID }}(w http.ResponseWriter, r *http.Request{{ range .PathParams }}, {{ .GoVariableName }} {{ .TypeDecl }}{{ end }}{{ if .HasParams }}, params {{ .ParamsTypeName }}{{ end }})
 {{- end }}
 }
-
-// Unimplemented server implementation that returns http.StatusNotImplemented for each endpoint.
-type Unimplemented struct{}
-
-{{- range . }}
-{{ .SummaryAsComment }}
-// ({{ .Method }} {{ .Path }})
-func (_ Unimplemented) {{ .GoOperationID }}(w http.ResponseWriter, r *http.Request{{ range .PathParams }}, {{ .GoVariableName }} {{ .TypeDecl }}{{ end }}{{ if .HasParams }}, params {{ .ParamsTypeName }}{{ end }}) {
-	w.WriteHeader(http.StatusNotImplemented)
-}
-{{- end }}

experimental/examples/petstore-expanded/echo-v4/server/server.gen.go

@@ -11,14 +11,3 @@ type ServerInterface interface {
 	{{ .GoOperationID }}(ctx echo.Context{{ range .PathParams }}, {{ .GoVariableName }} {{ .TypeDecl }}{{ end }}{{ if .HasParams }}, params {{ .ParamsTypeName }}{{ end }}) error
 {{- end }}
 }
-
-// Unimplemented server implementation that returns http.StatusNotImplemented for each endpoint.
-type Unimplemented struct{}
-
-{{- range . }}
-{{ .SummaryAsComment }}
-// ({{ .Method }} {{ .Path }})
-func (_ Unimplemented) {{ .GoOperationID }}(ctx echo.Context{{ range .PathParams }}, {{ .GoVariableName }} {{ .TypeDecl }}{{ end }}{{ if .HasParams }}, params {{ .ParamsTypeName }}{{ end }}) error {
-	return ctx.NoContent(http.StatusNotImplemented)
-}
-{{- end }}

experimental/examples/petstore-expanded/echo/server/server.gen.go

@@ -11,14 +11,3 @@ type ServerInterface interface {
 	{{ .GoOperationID }}(ctx *echo.Context{{ range .PathParams }}, {{ .GoVariableName }} {{ .TypeDecl }}{{ end }}{{ if .HasParams }}, params {{ .ParamsTypeName }}{{ end }}) error
 {{- end }}
 }
-
-// Unimplemented server implementation that returns http.StatusNotImplemented for each endpoint.
-type Unimplemented struct{}
-
-{{- range . }}
-{{ .SummaryAsComment }}
-// ({{ .Method }} {{ .Path }})
-func (_ Unimplemented) {{ .GoOperationID }}(ctx *echo.Context{{ range .PathParams }}, {{ .GoVariableName }} {{ .TypeDecl }}{{ end }}{{ if .HasParams }}, params {{ .ParamsTypeName }}{{ end }}) error {
-	return ctx.NoContent(http.StatusNotImplemented)
-}
-{{- end }}