Actus 1.4.0

Added

• routing::covering_family(mount, prefixes) (and routing::family_segments),
  re-exported at actus::routing: which family covers a mount, by the exact
  rule the families block of app_routes! applies at compile time —
  segment-aligned, longest prefix wins, * sugar, root covers all. A boot-time
  coverage check written against it cannot disagree with the compile-time one.
  Consumers had been re-deriving the rule as mount.split('/').next(), which
  agrees only while every family is a single segment and diverges silently the
  moment one nests — found in production the first time a family was nested.
  The README snippet and examples/advanced now use it.