## Why
Shell startup can copy a credential into another variable and unset its original source. These aliases need credential brokering without losing source restrictions or mistaking ordinary shell content for credentials.
## What changed
- Discover supported GitHub and OpenAI credentials embedded in environment values, even without their canonical variables. Preserve source ownership so unbound enterprise tokens cannot acquire a default host binding.
- Redact unregistered supported credentials during text virtualization, distinguish adjacent credentials, and avoid matching unrelated provider prefixes and common hashed paths.
- Expose helpers for checking allowed credential sources and restoring known dummy credentials in trusted text for fail-open execution.
- Render allowed credential aliases as snapshot exports and replace known credential values in shell state, preserving exported functions and credential-shaped function names.
## Testing
Add regression coverage for copied aliases, enterprise host binding, source filtering, adjacent tokens, path false positives, and dummy restoration. Add a Bash snapshot test that preserves exported functions while replacing credentials in heredoc content.
GitOrigin-RevId: f1c3d531405a96ac6bfa3882a11b74643fa6f123
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