add fleet-server and elastic-agent release notes (#1830)

Author: colleenmcginnis

config/assembler.yml

@@ -21,7 +21,7 @@ environments:
       cookies_win: x
     feature_flags:
       SEARCH_OR_ASK_AI: true
-  edge: 
+  edge:
     uri: https://d34ipnu52o64md.cloudfront.net
     path_prefix: docs
     content_source: edge
@@ -94,12 +94,14 @@ references:
   ecs-logging-python:
   ecs-logging-ruby:
   ecs-logging:
+  elastic-agent:
   elastic-otel-dotnet:
   elastic-otel-java:
   elastic-otel-node:
   elastic-otel-php:
   elastic-otel-python:
   elastic-serverless-forwarder:
+  fleet-server:
   integration-docs:
     private: true
   integrations:

config/navigation.yml

@@ -80,10 +80,13 @@ toc:
       - toc: kibana://release-notes
         path_prefix: release-notes/kibana
 
-      # Fleet and Elastic Agent
-      # https://github.com/elastic/docs-content/blob/main/release-notes/fleet-elastic-agent/toc.yml
-      - toc: docs-content://release-notes/fleet-elastic-agent
-        path_prefix: release-notes/fleet
+      # Elastic Agent
+      - toc: elastic-agent://release-notes
+        path_prefix: release-notes/elastic-agent
+
+      # Fleet Server
+      - toc: fleet-server://release-notes
+        path_prefix: release-notes/fleet-server
 
       # Logstash
       # https://github.com/elastic/logstash/blob/main/docs/release-notes/toc.yml
@@ -107,7 +110,7 @@ toc:
       # https://github.com/elastic/cloud/blob/master/docs/docset.yml
       - toc: cloud://release-notes/cloud-hosted
         path_prefix: release-notes/cloud-hosted
-        
+
       # Cloud Enterprise
       # https://github.com/elastic/cloud/blob/master/docs/release-notes/cloud-enterprise/toc.yml
       - toc: cloud://release-notes/cloud-enterprise
@@ -131,7 +134,7 @@ toc:
           # EDOT iOS / Swift
           # https://github.com/elastic/apm-agent-ios/blob/main/docs/release-notes/toc.yml
           - toc: apm-agent-ios://release-notes
-            path_prefix: release-notes/edot/sdks/ios         
+            path_prefix: release-notes/edot/sdks/ios
           # EDOT Java
           # https://github.com/elastic/elastic-otel-java/blob/main/docs/release-notes/toc.yml
           - toc: elastic-otel-java://release-notes
@@ -308,7 +311,7 @@ toc:
           # https://github.com/elastic/elasticsearch/blob/main/docs/reference/elasticsearch-plugins/toc.yml
           - toc: elasticsearch://reference/elasticsearch-plugins
             path_prefix: reference/elasticsearch/plugins
-          
+
       # Security
       # https://github.com/elastic/docs-content/blob/main/reference/security/toc.yml
       - toc: docs-content://reference/security