Do we need Static / StaticFS / StaticFile / StaticFileFS on the router?

[qm012]

Motivation

sim is a thin wrapper over net/http.ServeMux, so static file serving
already works today via raw stdlib composition:

app := sim.NewApp()                                                                                                                                                  
app.Handle("GET /static/", http.StripPrefix("/static/", http.FileServer(http.Dir("public"))))                                                                        

Do we want dedicated helpers at all — and if so, how many? Every method added to the API surface is a contract we maintain: docs, tests, and
naming decisions all follow.

How other frameworks do it (verified from source)

Framework	Methods	Directory listing default	index.html
gin	Static / StaticFS / StaticFile / StaticFileFS	disabled (Dir(root,false)/OnlyFilesFS)	yes
echo	Static / StaticFS / File / FileFS	none (never enumerates)	yes
fiber	Static (1, config-driven)	disabled (Browse:false, opt-in)	yes (Index:"index.html")
chi / mux	—	stdlib default (enabled)	yes