feat: add deterministic PII PHI redaction gate

[0xMudit]

Summary

Public Boundary

• This change does not include PII, PHI, secrets, keys, tokens, raw private transcripts, private screenshots, or private customer/patient data.
• Examples, fixtures, personas, screenshots, and artifact snippets are synthetic or redacted.
• Product-specific private context stays outside this repository or in synthetic adapter fixtures only.

Proof

Remaining Gaps