Phase 1, Task 1.1. New package hermes_cli/dashboard_auth/ contains:
base.py - DashboardAuthProvider ABC with 5 abstract methods
(start_login, complete_login, verify_session,
refresh_session, revoke_session), Session + LoginStart
frozen dataclasses, three exception types
(ProviderError / InvalidCodeError / RefreshExpiredError),
and assert_protocol_compliance() for plugins to call
in their own tests.
registry.py - Module-level register/get/list/clear with a lock.
Nothing reads the registry yet — Phase 2 adds the StubAuthProvider and
Phase 3 wires the gate middleware. The plugin hook lands in Task 1.3.
