release(v4.9.0): relay-side encrypted blob primitive + SDK Profile namespace

Ships the Prism FR (encrypted-profile-storage-v4.9.md) as a generic
relay-side encrypted blob primitive: deterministically-located,
AEAD-sealed blobs keyed by a 32-byte slotId derived client-side via
HKDF from the user's master key. Unlocks credential-only bootstrap
of new devices into existing E2EE state — no QR, no physical access.

Server: BlobStore interface + Memory/Sqlite/Postgres impls,
createBlobRoutes for GET/PUT/DELETE /v1/blob/:slotId with TOFU pubkey
auth and If-Match CAS (409/412 semantics). Mounted on the same Hono
app as the inbox; SHADE_BLOB_PG_URL / SHADE_BLOB_DB_PATH /
SHADE_DISABLE_BLOB env-var plumbing in standalone.

SDK: createProfileNamespace high-level wrapper (HKDF derivation,
random-nonce AEAD seal, slotId-bound AAD) + low-level BlobClient.
Cross-platform test vectors in test-vectors/blob-storage.json.

New errors: ConflictError (409), PreconditionFailedError (412).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/shade-storage-encrypted/src/crypto/kdf.ts

@@ -122,3 +122,42 @@ export function deriveNonce(rowKey: Uint8Array, table: string, pk: string): Uint
 export function buildAad(table: string, column: string, pk: string): Uint8Array {
   return TEXT.encode(`shade-aad-v1|${table}|${column}|${pk}`);
 }
+
+// ─── V4.9 — relay-side encrypted blob primitive ──────────────
+//
+// Three deterministic 32-byte derivations rooted at the user's master
+// key, used by `@shade/sdk`'s `Profile` namespace to bootstrap a brand
+// new device into existing E2EE state from credentials alone:
+//
+//   slotId    = HKDF(masterKey, info=`shade-blob-slot-v1:${app}`)
+//   blobKey   = HKDF(masterKey, info=`shade-blob-key-v1:${app}`)
+//   sigSeed   = HKDF(masterKey, info=`shade-blob-sig-v1:${app}`)
+//
+// `app` is a caller-supplied namespace (e.g. `"prism-profile"`) so two
+// Shade apps with the same user/master never collide on the same slot.
+//
+// The slot identifier and the AEAD key are *both* derived from the
+// master — the relay sees opaque slotIds and AEAD-sealed blobs and
+// cannot decrypt or correlate slots to users. The signing seed is the
+// raw 32-byte Ed25519 private key (matches @noble/curves' API: pubkey
+// = ed25519.getPublicKey(seed)).
+
+/** Lower-hex 64-char slotId derived from the master key. */
+export function deriveBlobSlotId(masterKey: Uint8Array, app: string): Uint8Array {
+  return hkdfDerive(masterKey, `shade-blob-slot-v1:${app}`, 32);
+}
+
+/** AEAD key for sealing/opening the blob. Use AAD = slotId. */
+export function deriveBlobKey(masterKey: Uint8Array, app: string): Uint8Array {
+  return hkdfDerive(masterKey, `shade-blob-key-v1:${app}`, 32);
+}
+
+/**
+ * 32-byte Ed25519 signing seed (== the private key in the @noble/curves
+ * convention). The pubkey, derived deterministically from the seed, is
+ * what the relay TOFU-stores on the first PUT and verifies subsequent
+ * writes against.
+ */
+export function deriveBlobSigningSeed(masterKey: Uint8Array, app: string): Uint8Array {
+  return hkdfDerive(masterKey, `shade-blob-sig-v1:${app}`, 32);
+}