Use full 'Namespace', HTML bold for active-Cluster notes, rename final note

- Expand 'ns' to 'Namespace' in the sequence diagram participants.
- Bold the active-Cluster notes with <b> (markdown strings rendered literally).
- Rename the final note to 'Nexus Operation completes'.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: stephanos

docs/production-deployment/self-hosted-guide/temporal-nexus.mdx

@@ -141,21 +141,21 @@ after it, on the new active Cluster:
 ```mermaid
 sequenceDiagram
     box Cluster A
-    participant caA as Caller ns
-    participant haA as Handler ns
+    participant caA as Caller Namespace
+    participant haA as Handler Namespace
     end
     box Cluster B
-    participant caB as Caller ns
-    participant haB as Handler ns
+    participant caB as Caller Namespace
+    participant haB as Handler Namespace
     end
-    Note over caA,haA: Cluster A active
+    Note over caA,haA: <b>Cluster A active</b>
     caA->>haA: start Nexus Operation
     haA-->>caA: Operation started, token returned
     Note over caA,haB: Namespace state replicates A to B
     Note over caA,haB: 💥 failover, active moves to Cluster B
-    Note over caB,haB: Cluster B active
+    Note over caB,haB: <b>Cluster B active</b>
     haB->>caB: completion delivered (callback)
-    Note over caB: Caller Workflow completes
+    Note over caB: Nexus Operation completes
 ```
 
 - **Callbacks are delivered internally** to the caller Namespace's active Cluster,