docs(adrs): reconcile WS-03 browser data-channel promise (ADR-067/048)

Record the v1 cut for browser-opened data channels over WS (review-001
WS-03): the design (ADR-067) stands; only the wiring is deferred.

- open-questions.md: add OQ-05 (deferred(scope: v1 cut)) with gap
  detail and deferred scope
- ADR-067: dated status amendment + v1-cut note at the data-channel
  step; References point to OQ-05
- ADR-048: dated reconciliation note — overlay bidirectionality is
  decided design, not a v1 implementation commitment
- websocket.md: status notes on §"Data channels for browsers" and
  upgrade step 7
- task review-001-ws-data-channel-decision: completed, Summary filled

Verification: taskgraph validate (38 tasks OK); cargo doc --no-deps
(pre-existing warnings only).

docs/architecture/decisions/048-websocket-native-session-not-gateway.md

@@ -6,6 +6,16 @@
 
 Accepted
 
+> **Reconciliation note (2026-08-29):** the bidirectionality this ADR
+> promises for the WS path (§4 — the hub calling browser-registered ops
+> through the connection-local Layer 2 overlay) is **decided design,
+> not a v1 implementation commitment**. Today the WS path installs
+> channel 0 only; no data-channel open path and no browser-side
+> registration wiring exists (review-001 finding WS-03). The cut and
+> its rationale are recorded in
+> [OQ-05](../open-questions.md); the native-session contract below
+> stands as what the deferred wiring must satisfy.
+
 ## Status amendment (alkhttp port)
 
 - **The WS path carries the channels session** (alkhttp ADR-067): a