[M5] mxaccess: F26 step 3 — AsbSession high-level cheap-clone async API

Adds the public high-level entry point for the ASB transport.
Parallel to the NMX-shaped `Session` (rather than unified) because
NMX's `Session` carries CallbackExporter / callback router task /
recovery broadcast / INmxService2 mutex orchestration that has no
ASB analogue — and ASB's request/response loop over a single TCP
stream maps naturally to `Mutex<AsbClient>` that would be foreign
to NMX. Two paths converge at the consumer-facing API but stay
distinct at the orchestration layer.

Struct shape:
```rust
pub struct AsbSession { inner: Arc<AsbSessionInner> }
struct AsbSessionInner {
    transport: Mutex<AsbTransport<TcpStream>>,
    connect_response: ConnectResponse,
}
```

`Clone + Send + Sync` — clones share state through `Arc`, lock
serialises operations. Compile-time `assert_clone_send_sync` test
guards the contract.

API:
* `connect(endpoint, passphrase, crypto_parameters, via_uri,
  connection_id)` — full bring-up (TCP + preamble + DH handshake).
* `from_transport(transport, connect_response)` — build from an
  existing transport (tests, custom transports).
* `connect_response()` — surface the negotiated lifetime /
  Apollo flag.

Operation methods forward to AsbClient:
* `register_items` / `unregister_items` / `read` / `write`
* `keep_alive` / `disconnect`
* `create_subscription` / `add_monitored_items` / `publish` /
  `delete_monitored_items` / `delete_subscription`
* `publish_write_complete`

ClientError → mxaccess::Error mapping via
`ConnectionError::TransportFailure` (consistent with F26 step 2).

1 new test:
* `asb_session_is_clone_send_sync` — compile-time trait-bound
  assertion.

Workspace: 702 tests pass.

Stubbed for next F26 iteration:
* `Stream<Item = MonitoredItemValue>` subscription handle that
  internally drives a publish-loop. Today consumers loop
  `publish().await` themselves.
* Recovery / reconnect policy — needs a captured ASB-side
  disconnect to inform the retry strategy.
* Live-probe wire-byte reconciliation against the WCF DataContract
  XML serializer's actual output.

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

design/followups.md

@@ -46,7 +46,11 @@ move to `## Resolved` with a date + commit hash.
 
 **Resolves when:** F19-F26 are all closed and the four DoD bullets above pass.
 
-**Cumulative execution log.** F19 + F23 (`ed17c07`); F24 (`7611d9e`); F20 (`9dfd193`); F22 (`43c10a1`); F21 (`5f98558`); F25 step 1 (`25dbd8d`); F25 step 2 (`a2b8989`); F25 step 3 (`c4bf0a0`); F25 step 4 (`1e59249`); F25 step 5 (`9b8133f`); F25 step 6 (`321b796`); F25 step 7 (`1b1ee1e`); F26 step 1 (`8a0f92b`); F26 step 2 (`14bb529`); example rewrite (`c6570dc`); F25 step 8 (`b543eb1`); F25 step 9 (`0441a2e`); F25 step 10 landed in this commit:
+**Cumulative execution log.** F19 + F23 (`ed17c07`); F24 (`7611d9e`); F20 (`9dfd193`); F22 (`43c10a1`); F21 (`5f98558`); F25 step 1 (`25dbd8d`); F25 step 2 (`a2b8989`); F25 step 3 (`c4bf0a0`); F25 step 4 (`1e59249`); F25 step 5 (`9b8133f`); F25 step 6 (`321b796`); F25 step 7 (`1b1ee1e`); F26 step 1 (`8a0f92b`); F26 step 2 (`14bb529`); example rewrite (`c6570dc`); F25 step 8 (`b543eb1`); F25 step 9 (`0441a2e`); F25 step 10 (`9876b4e`); F26 step 3 landed in this commit:
+- F26 step 3: `mxaccess::AsbSession` — high-level cheap-clone async API on top of `AsbTransport`. Parallel to the NMX-shaped `Session` rather than unified, because NMX's `Session` carries orchestration (`CallbackExporter`, callback router task, recovery broadcast, `INmxService2` mutex) that has no ASB analogue, and ASB's request/response loop over a single TCP stream maps naturally to a `Mutex<AsbClient>` that would be foreign to NMX. The struct is `Clone + Send + Sync` (compile-time `assert_clone_send_sync` test guards the contract) — clones share inner state through `Arc<AsbSessionInner { transport: Mutex<AsbTransport<TcpStream>>, connect_response }>`, so each `clone()` is `O(1)` and the lock serialises operation calls. API surface: `AsbSession::connect(endpoint, passphrase, crypto_parameters, via_uri, connection_id)` runs the full bring-up; `from_transport(transport, connect_response)` builds from an existing transport for tests; `connect_response()` exposes the negotiated lifetime / Apollo flag. Operation methods forward to AsbClient: `register_items`/`unregister_items`/`read`/`write`/`keep_alive`/`disconnect`/`create_subscription`/`add_monitored_items`/`publish`/`delete_monitored_items`/`delete_subscription`/`publish_write_complete`. ClientError → mxaccess::Error mapping via `ConnectionError::TransportFailure` (consistent with F26 step 2). 1 new test (compile-time Clone+Send+Sync assertion). **Stubbed for next F26 iteration**: `Stream<Item = MonitoredItemValue>` subscription handle that internally drives a publish-loop, recovery/reconnect policy, and full live-probe wire-byte reconciliation. Workspace: 702 tests pass.
+
+**Earlier slices:**
+- F25 step 10 (commit `9876b4e`):
 - F25 step 10: PublishWriteComplete + DeleteMonitoredItems — closes out the F25 operation matrix. `build_publish_write_complete_request_body` emits the empty wrapper element per `AsbContracts.cs:204-205` (no body fields beyond ConnectionValidator). `decode_publish_write_complete_response` returns a count of `<ItemWriteComplete>` elements observed; per-element decode (Status array + WriteHandle) is deferred to a later iteration since `ItemWriteComplete` is regular WCF DataContract rather than the binary fast-path. `build_delete_monitored_items_request_body` mirrors AddMonitoredItems but omits the RequireId field per `cs:268-277`. `decode_delete_monitored_items_response` returns the per-item Status array. Two new client wrappers: `publish_write_complete()` and `delete_monitored_items(subscription_id, items)`. 6 new tests cover empty-body shape, ItemWriteComplete counting (0 / 2 elements), DeleteMonitoredItems body shape (carries SubscriptionId + MonitoredItem), DeleteMonitoredItems omits RequireId, and Status round-trip. **F25 operation matrix complete**: AsbClient now wraps every IASBIDataV2 operation: `connect`/`disconnect`/`send_end`/`send_preamble`/`keep_alive` (lifecycle), `register_items`/`unregister_items`/`read`/`write` (items), `create_subscription`/`add_monitored_items`/`publish`/`delete_monitored_items`/`delete_subscription` (subscriptions), `publish_write_complete` (write callback). Workspace: 701 tests pass (was 695, +6).
 
 **Earlier slices:**