Two credential patterns were missing from the PiiDetector, confirmed
by live audit log showing was_pii_redacted: false with plaintext creds:
1. Abbreviated key form (pass: abc123!!): the pattern only matched
password|passwd|pwd. Added pass, passphrase, secret with a word
boundary to prevent substring false positives (bypass:, compass:).
2. Natural language form (Is the password password123 good): added a
second Password sub-pattern for keyword-adjacent values without a
key separator. Value must contain a digit or special char to avoid
flagging plain words (password strength, password policy).
5 new regression tests added. 233/233 Rust tests pass.
