fix(up-03): PeerCompositeEnv::peer_operations override — list-peers sees peer-announced ops

Surfaced by alkhttp review 006 (UP-03): services/list-peers showed
every peer with an empty operations array. PeerCompositeEnv overrode
peer_ids only, so peer_operations fell to the trait default
(Vec::new()) and the ADR-022 amendment's "announced op is discoverable
via services/list-peers" promise never resolved on the wire. ADR-030
prescribed the fix but it had never been ported into alkcall. The
existing list-peers unit tests passed because they mock
peer_operations with hand-rolled envs.

Implements ADR-030 as specified:
- OperationEnv gains list_operation_names (default Vec::new(),
  back-compat for all existing implementors)
- OverlayOperationEnv overrides it with its overlay's registered names
- PeerCompositeEnv::peer_operations delegates to the peer overlay's
  list_operation_names; PeerCompositeEnv::list_operation_names
  aggregates session + connections + base (mirrors its contains())
- LocalOperationEnv enumerates its registry; ChannelsSessionEnv
  delegates to base

Gate: announced_op_is_discoverable_via_services_list_peers in
src/registry/op_register.rs — announces an op through op/register,
then asserts both the direct peer_operations probe and the
services/list-peers wire shape attribute the announced op to the peer,
over the exact compose_root_env shape (PeerCompositeEnv + attached
connection overlay). Verified load-bearing: reverting the
peer_operations override fails the gate.

ADR-030 status Proposed -> Accepted with the UP-03 provenance note.

Verification: 590 default / 607 all-features tests, clippy
(all-targets, all-features, wasm32) clean, fmt clean, doc clean,
semver-checks 196 pass against v0.3.0 (defaulted trait method is
non-breaking).

src/channels/env.rs

@@ -83,6 +83,10 @@ impl OperationEnv for ChannelsSessionEnv {
         self.base.peer_operations(peer)
     }
 
+    fn list_operation_names(&self) -> Vec<String> {
+        self.base.list_operation_names()
+    }
+
     async fn invoke_peer(
         &self,
         peer: &crate::registry::env::PeerRef,