* Fix get_* returning None when latest version is disabled (#3421)
When a visibility transform disabled the highest version of a component,
get_tool/get_resource/get_resource_template/get_prompt returned None
instead of falling back to the next-highest enabled version. The list_*
path already worked correctly because deduplication runs after visibility
filtering. The get_* path now falls back to listing all versions and
picking the highest enabled one when the top version is disabled.
* Apply auth checks in version fallback paths
The fallback code in get_tool, get_resource, get_resource_template, and
get_prompt bypassed auth filtering when falling back to older versions
after the highest version was disabled. This could expose auth-protected
older versions to unauthorized users.
