release(v4.11.0): streaming Double-Ratchet sub-sessions (ShadeStream)

Answers Vyvern FR shade-ws-streaming-ratchet.md with a first-class
streaming-session API rather than the documented-contract fallback.
The Double-Ratchet crypto was already safe for high-frequency
one-directional use; the send/receive wrapper was not (per-frame
saveSession keystore write; shared per-peer mutex + single stored
session row coupling reuse to the HTTP path).

- @shade/core: stream.ts — identity-bound 3-DH seeding (X3DH-minus-
  prekeys, no prekey-server round trip, mutually authenticated against
  the parent session's pinned identities), bootstrapStreamSession
  reusing init{Sender,Receiver}Session verbatim, in-memory-only
  StreamRatchet (own op-mutex, never persisted, zeroized on close).
  beginStream/acceptStream on ShadeSessionManager; Stream{Closed,
  Handshake}Error; stream.opened/closed events.
- @shade/proto: STREAM_OPEN/OPEN_ACK/FRAME wire (0x31/0x32/0x33),
  additive; inspectEnvelopeType extended.
- @shade/sdk: Shade.openStream/acceptStream → ShadeStream
  (handshakeFrame/handleHandshake/seal/open/close), transport-
  agnostic, independent of encrypt/decrypt queues + parent session,
  identical server (sqlite:) and browser (IndexedDB) — touches no
  storage.
- Tests: 5000-frame one-directional burst (bounded skipped keys + FS
  zeroize), parent-session independence, replay/rewind rejection,
  mutual-auth, proto wire round-trips. Full suite green (1159 pass).
- docs/streaming-sessions.md (R1–R7 contract); SECURITY.md matrix rows.

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

packages/shade-server/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@shade/server",
-  "version": "4.10.0",
+  "version": "4.11.0",
   "type": "module",
   "main": "src/index.ts",
   "types": "src/index.ts",