Storage Engine

• Header: magic ("Aing"), version, 16‑byte salt, KDF kind, cipher.
• Encryption: configurable cipher (aes-256-gcm, chacha20-poly1305, xchacha20-poly1305) and KDF (scrypt or argon2id). Provide passphrase to enable at rest encryption.
• Indexes: vector (HNSW), full‑text (FTS), and spatial (R‑Tree) registries auto‑maintain on insert/delete.
• Compaction: db.compact() rewrites a checkpoint and prunes WAL.
• TTL: rows expire when the configured ttl.column evaluates to a past time.