- Add lastKnownCloudRoleProvider, which caches the last non-null header
  role for the open strategy and resets only when a different strategy
  is opened. The editor's "View only" chip now reads this instead of
  remoteStrategySnapshotProvider.valueOrNull, so it no longer flickers
  off during transient snapshot reloads, refresh errors, or auth
  incidents; it is absent only before the role has ever been known.
- Document that cloudBadgeKindForRole's unknown-role fallback to the
  viewer badge deliberately mirrors StrategyCapabilities.fromCloudRole,
  which grants viewer capabilities to any role that is not exactly
  'owner' or 'editor'.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>