Railbase core v0.5.16

Marketplace + launcher fixes.

• marketplace: data-resident (kind:js) plugins now show as installed in the in-core Plugin Marketplace (the installed-list previously only knew OOP/backend plugins).
• cli: a bare railbase on an already-initialized site (existing data dir/vault) now starts the backend directly instead of re-showing the first-run menu; fresh installs still get the guided menu; non-TTY unchanged.
• admin: internal eslint cleanup (theme tokens; no behavior change).