release(v4.0.0): Shade GA — V3.x consolidation + audit prep

V3.1 → V3.12 consolidated and tagged for the first GA release. Wire
format unchanged from 0.4.x — 4.0 peers interoperate with 0.4.x peers
byte-for-byte. The version bump is semantic: audit-cycle complete,
opt-in surface fully exposed, threat model refreshed for every new
surface.

Highlights:
- All 24 @shade/* packages bumped to 4.0.0 in lockstep.
- CHANGELOG 4.0.0 section is the canonical manifest of what landed.
- THREAT-MODEL extended (§10 fingerprint gates, §11 WebRTC P2P, §12
  Web-Worker boundary) + residual-risks table refreshed.
- OpenAPI now covers all 27 routes: prekey, transfer, KT, inbox,
  bridge, observer, /metrics, /healthz, /ready.
- MIGRATION 0.3.x → 4.0 documented + smoke-tested against
  shade migrate-storage on a real SQLite DB.
- docs/audit/REVIEW-BUNDLE.md + SCOPE.md ready for external reviewer.
- scripts/soak.ts harness for the GA-stable 2-week soak window.
- All V*.md plans archived under docs/archive/ with Status: Done.
- Voice/Video carved out into V5.0; 4.0 audit focuses on the frozen
  non-realtime stack.

Tests: TS 1000/1000 + Kotlin 11/11 cross-platform vectors green.
Docker: gt.zyon.no/stian/shade-prekey:4.0.0 builds and reports
  version 4.0.0 on /health.

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

docs/files.md

@@ -193,9 +193,28 @@ VERSION was bumped from `0x01` to `0x02` to lift the 64 KiB length-prefix
 ceiling that previously capped ratchet payloads. **Sessions are
 incompatible across the bump**; both peers must run 0.3.0+.
 
+## Rich file metadata + previews (V3.9)
+
+`stream-init` carries optional E2EE `fileMetadata` (filename, MIME,
+thumbnail-stream pointer). `@shade/files` consumers see this on the
+incoming-transfer side and can render previews via `<TransferRow
+showThumbnail />`. The thumbnail itself rides as a separate AEAD
+stream — server never sees preview pixels in plaintext.
+
+See [streams.md § Rich file metadata + previews](streams.md#rich-file-metadata--previews-v39)
+for the wire format, format-hardening rules, and renderer trust
+model. The pattern integrates seamlessly with `@shade/files`'s own
+write/read RPCs — pass `fileMetadata` in the underlying
+`shade.upload` and the same `ShadeThumbnailCache` powers previews
+across all transfer surfaces.
+
 ## Related modules
 
 * `@shade/streams` — chunk encryption, lane key derivation. Indirect dep.
 * `@shade/transfer` — multi-lane transport with HTTP / WS fallback.
+* `@shade/transport-webrtc` (V3.11, optional) — direct P2P chunk
+  delivery via `RTCDataChannel`; large `read`/`write` payloads
+  automatically prefer WebRTC when both peers have called
+  `shade.configureWebRTC()`.
 * `@shade/sdk` — `Shade.files` getter; `BackgroundHooks.onPruneFiles` for
   retention.