Low‑Entropy PII Torture Vector (ciphertext‑only exposure)

[flyingrobots]

Goal
Prove that pointers for low‑entropy PII do not expose plaintext digest and DO include ciphertext_digest per policy class.

Acceptance Criteria

• Add test vectors (emails, phone numbers, short strings).
• When privacy class pii_low_entropy is applied, public projection omits digest and includes ciphertext_digest.
• Negative case: CI test fails if digest appears in public pointer for a low‑entropy field.
• Document how to classify additional selectors via policy.

Notes

• Reference: ADR‑0004 Policy Hooks; governance_policy schema extension.