admin: name attached scopes on environments and tag attached scope rows (#533)

* admin: name attached scopes on environments and tag attached scope rows

The scope index's Named environments card previously showed only a count
of attached scopes; it now lists the attached scopes by name (first four,
then a +N overflow). Scope rows in the index also gain a small "env:"
tag when the scope is attached to a named environment, so it's visible at
a glance which scopes share a computer.

* admin: tooltip with the full attached-scope list + roster card on the environment page

- The Named environments card's preview keeps the truncated first-four
  view but now carries a title tooltip listing every attached scope.
- Opening a named environment's history page shows an "Attached scopes"
  card with a clickable chip per attached scope.

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Co-authored-by: Josh France <josh@ycombinator.com>