Store an already-encrypted memory

Blind vault: the client encrypts the content and sends an opaque blob. The server charges the same fee, anchors the hash and stores bytes it cannot read. Unlike a plaintext memory, the event_hash comes from the client, so a sealed memory is citable as evidence immediately. Requires a custodial key able to sign the anchor. Optional embedding (since 2026-09-21): the memory's search vector, computed on the client. With it the memory appears in semantic search without the server reading it; the response says so in searchable. Without it the memory is stored anyway, but it can only be found by project or tag.