fix(review 005 Unit 2): op/register serving-registry collision gate (G-03)

- op_register_handler takes the serving registry alongside the
  connection and rejects announced names that collide with the serving
  side's own registrations (ALREADY_EXISTS regardless of replace).
  Peer-announced ops may collide with peer-announced ops (replace
  governs, the reconnect path) but never shadow the deployment's own
  ops: the connection overlay resolves before base in PeerCompositeEnv,
  so an unscreened same-name announce would silently rewrite what a
  wire-dispatched handler's ctx.env.invoke resolves. Composition
  authority (ADR-018) stays with the deployer.
- ADR-022 amendment (2026-09-04): collision policy recorded in the
  2026-09-03 amendment's op/register section (rationale + visibility
  irrelevance); status line notes the sub-amendment.
- Gates: base-External collision rejected even with replace (overlay
  stays clean, serving registration untouched); Internal base op
  equally protected; overlay/overlay collisions still follow replace;
  nested composition of a base op resolves the serving side's own op
  after an unrelated announce (real compose_root_env env shape).
- PeerCompositeEnv resolution order deliberately unchanged.

Verification: cargo test 587 / --all-features 604, clippy
(all-targets, all-features, wasm32) clean, fmt clean, doc clean.

Refs docs/reviews/005-...md (G-03; Unit 3 open).

src/channels/client.rs

@@ -1458,6 +1458,7 @@ mod tests {
                         crate::registry::op_register::op_register_spec(AccessControl::default()),
                         HandlerKind::Once(crate::registry::op_register::op_register_handler(
                             Arc::clone(&call_connection),
+                            Arc::clone(&accept_registry),
                         )),
                         OperationProvenance::Local,
                         None,
@@ -1848,6 +1849,7 @@ mod tests {
                         crate::registry::op_register::op_register_spec(AccessControl::default()),
                         HandlerKind::Once(crate::registry::op_register::op_register_handler(
                             Arc::clone(&call_connection),
+                            Arc::clone(&accept_registry),
                         )),
                         OperationProvenance::Local,
                         None,