Addresses AI-review feedback on #94653: note where the 'connect-on-demand'
sentinel is produced, and cover the interaction between
isLocalEnumerationFailure and localRouteFallbackProfiles directly (not just
the helper in isolation).
'connect-on-demand' means local roster enumeration was intentionally
skipped to avoid spawning a local backend on a remote-only workspace,
not that it failed. The plugin-profile-routes IPC handler passed
Boolean(error) straight through, so that deferral was treated as a
genuine failure and Bot Mode re-synthesized cached local profile rows
even though local was never dialed.
Fixes#94648
chelsealong