## What changed
- Discover supported credentials inherited from the parent even when their canonical provider variable is filtered from the child environment.
- Replace matching values and credentials embedded in longer child environment values with broker dummies, then restore only aliases that the broker virtualized.
- Preserve provider and host bindings when selecting credentials for outbound requests, including GitHub Enterprise and custom OpenAI hosts.
- Expose helpers for identifying provider and binding variables, plus an API for virtualizing credential-bearing text before it is persisted.
## Testing
- Extend credential broker tests for filtered parent variables, exact and embedded aliases, text virtualization, user overrides, and host-bound GitHub and OpenAI credentials.
GitOrigin-RevId: 55d673911900470aab4e206d0f4f5e62ed3611ae