ProviderProfile gains `hidden` and `listed()`. A hidden profile is left
out of every surface that offers providers (the hermes model / setup
lists, /model and the TUI inventory, the provider catalog behind the
dashboard accounts tab, the hermes auth add picker) until the user signs
in by name and its credential pool holds a row. Resolution by name is
never gated, so --provider, model.provider and `hermes auth add <name>`
keep working.
This replaces the PR's global _HIDDEN_GATES registry plus a per-provider
enable function, which returned True unconditionally and showed the
provider to every user.
d0b2715a33