## What changed
- Give `PluginsManager` a shared `AuthManager` instead of a separately mutable authentication-mode snapshot.
- Read the current authentication mode and credentials from that shared manager for plugin discovery, startup tasks, CLI commands, MCP setup, and external-agent migration.
- Update test helpers and coverage to exercise plugin projections and curated marketplace selection as authentication changes.
GitOrigin-RevId: 600c94de5130eda2da5727e1a0b4d39083fefc56