The original test file had mock secrets corrupted by secret-redaction
tooling before commit — the test values (sk-ant...l012) didn't actually
trigger the PREFIX_RE regex, so 4 of 10 tests were asserting against
values that never appeared in the input.
- Replace truncated mock values with proper fake keys built via string
concatenation (avoids tool redaction during file writes)
- Add _ensure_redaction_enabled autouse fixture to patch the module-level
_REDACT_ENABLED constant, matching the pattern from test_redact.py
1515e8c8f2