GeezerVison

Active Admin pages render only ActiveAdmin.importmap and import only its
active_admin entry point, so a module pinned in the host's importmap loads
nothing. Themes and plugins copied _html_head to add their imports.

Co-Authored-By: Clanker

The setting default is one shared array, so appending to it leaked into every later Application.

Co-Authored-By: Clanker

Co-Authored-By: Clanker

Importmap::Map#cache_sweeper(watches:) builds a new watcher on each call,
so an engine that passed its own directory replaced ActiveAdmin's. The
sweeper is now built once in after_initialize from this list, which
engines and config/initializers can extend.

Co-Authored-By: Clanker

A request made from an earlier after_initialize hook ran before the
sweeper existed. The spec now edits an existing file instead of relying
on a new one, and restores the boot-time sweeper.

Co-Authored-By: Clanker

The sweeper reads the list once in after_initialize, so a directory
added later, for example from to_prepare, was silently never watched.

Co-Authored-By: Clanker

builder_method runs when the component class loads, and nothing
references the class constant, so autoloading never loads it before the
register blocks that use it.

Co-Authored-By: Clanker

Rails runs to_prepare blocks on the reloader, so a bare root is
undefined there, and appends to importmap_watches made after
after_initialize never reach the sweeper.

Co-Authored-By: Clanker

A plain frozen array already rejects late appends. The setting's comment
now says to append from an initializer.

Co-Authored-By: Clanker