Back-merge to resolve PR #2930 (release/v3.8.8 -> main) conflicts. Release is a
superset of main's features, so all ~44 content conflicts resolved to the
release ("ours") version; generated .source/* dropped.
Reconciliation:
- auth.ts: port #3058 (getProviderSearchPool expands custom provider_nodes
prefixes to internal connection ids) — release lacked this main fix.
- quota-plan-registry.test.ts: align knownProviders() 6 -> 10 (pre-existing
stale assertion vs the registry).
72b4804c1b