fix(dcl): route native OPC UA alarms by binding identity, not event name

A native OPC UA alarm source's SourceReference has to be two things at once:
it is parsed as a NodeId to open the monitored item, and matched as a plain-name
prefix against the event's SourceName to route the transition to an instance. No
string is both, so a NodeId-form binding subscribed correctly and then silently
dropped every transition — "pymodbus/plc/HR200".StartsWith("nsu=...;s=pymodbus/plc/HR200")
is false. Only the empty (Server-object) binding worked, because StartsWith("")
matches everything, which is why the sole live smoke test never caught it.

Each OPC UA alarm feed is opened for exactly one binding, so every transition on
it belongs to that binding. The adapter now tags each transition's routing
identity (SourceObjectReference) with the binding string verbatim via the pure
OpcUaAlarmMapper.BuildIdentity, making DataConnectionActor's routing key an exact
match regardless of whether the binding is stored as ns=<index> or the durable
nsu=<uri> form. The Server-object aggregate feed keeps an empty routing identity,
so it reaches only "mirror everything" subscribers and never leaks into a
specific-node binding. The per-condition SourceReference key stays the readable
SourceName.ConditionName, so persistence and display are unchanged, and MxGateway
is untouched — its bindings are names and its mapper already emits matching names.

Unblocked by lmxopcua#473 (OtOpcUa now populates SourceNode/SourceName/EventType
on conditions); SourceName is the RawPath, so the per-condition key is unique.
Live end-to-end verification against native alarms still needs a v3 rig.

Fixes: Gitea #17

docs/requirements/Component-DataConnectionLayer.md

@@ -254,7 +254,9 @@ Other/custom protocols do not implement the capability; a subscribe request agai
 
 ### Connection Actor Behavior
 
-The `DataConnectionActor` opens **one alarm feed per connection** (not per subscriber) and routes incoming transitions to instance subscribers by **source-object reference** — a prefix match of the transition's `SourceObjectReference` (falling back to `SourceReference`) against each subscriber's registered `SourceReference`. Subscribers (the Site Runtime's `NativeAlarmActor` instances) are **ref-counted per source**, so the underlying feed is opened once and torn down only when the last subscriber for that source unsubscribes.
+The `DataConnectionActor` opens **one alarm feed per source** (not per subscriber) and routes incoming transitions to instance subscribers by **source-object reference** — a prefix match of the transition's `SourceObjectReference` (falling back to `SourceReference`) against each subscriber's registered `SourceReference`. Subscribers (the Site Runtime's `NativeAlarmActor` instances) are **ref-counted per source**, so the underlying feed is opened once and torn down only when the last subscriber for that source unsubscribes.
+
+The registered `SourceReference` is a **NodeId** for OPC UA (the picker, CSV and config all store NodeIds), so the transition's routing identity must live in the same space or nothing matches. **Gitea #17**: the OPC UA adapter previously set `SourceObjectReference` from the event's `SourceName` (a plain name — the RawPath for OtOpcUa), which never prefix-matches a NodeId binding, so every native OPC UA alarm transition was silently dropped. Because each OPC UA feed is opened for exactly one binding, the adapter now tags every transition on that feed with the **binding string verbatim** (via the pure `OpcUaAlarmMapper.BuildIdentity`), making the routing key an exact match independent of whether the binding is stored as `ns=<index>` or the durable `nsu=<uri>` form. The Server-object aggregate feed (empty binding) keeps an empty routing identity, so it reaches only "mirror everything" subscribers and never leaks into a specific-node binding. The per-condition `SourceReference` key stays the human-readable `SourceName.ConditionName`, so persistence and display are unchanged. MxGateway is unaffected — its bindings are object names and its mapper already emits matching names.
 
 - **State gating**: `SubscribeAlarmsRequest` is handled only in the **Connected** state; requests arriving while **Connecting**/**Reconnecting** are stashed (standard Become/Stash) and processed on entering Connected.
 - **Capability check**: if `_adapter is not IAlarmSubscribableConnection`, the actor replies `SubscribeAlarmsResponse(Success = false, ...)`.