Encryption

TODO: this page will document the encryption model: PBKDF2-HMAC-SHA256 key derivation (600 K iterations), SQLCipher for the relational store, AES-GCM for recovery payloads, HMAC integrity tags for posture markers, keychain handling, and how the passphrase is collected and rotated.

Be precise but not so precise that we leak attack surface. All crypto string constants use the creativemachines/ namespace (rebrand-safe – see memory/feedback_brand_neutral_crypto_constants.md).

Owner: @andy. Cross-reference: ostler_security/ module, the 109 security tests, and the feedback_no_silent_security_fallback.md guidance (security-critical imports must hard-fail, never silently degrade).