Fix ConceptLink warnings in virt/post_installation_configuration

Move links and cross-references from main content to Additional resources
section to fix AsciiDocDITA.ConceptLink warnings.

Changes:
- Added [id="additional-resources_{context}"] attribute to Additional
  resources section in virt-post-install-config.adoc
- Updated link text to match actual heading titles from target files:
  * "Node placement rules..." → "Specifying nodes for {VirtProductName} components"
  * "Network configuration" → "Postinstallation network configuration"
  * "Storage configuration" → "Postinstallation storage configuration"
- Replaced inline xrefs with plain text in main content
- Moved 3 xrefs to Additional resources section

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: abrennan89

virt/post_installation_configuration/virt-post-install-config.adoc

@@ -17,9 +17,9 @@ endif::openshift-enterprise[]
 
 * The hostpath provisioner is a local storage provisioner designed for {VirtProductName}. If you want to configure local storage for virtual machines, you must enable the hostpath provisioner first.
 
-* xref:../../virt/post_installation_configuration/virt-node-placement-virt-components.adoc#virt-node-placement-virt-components[Node placement rules for {VirtProductName} Operators, workloads, and controllers]
+* Node placement rules for {VirtProductName} Operators, workloads, and controllers.
 
-* xref:../../virt/post_installation_configuration/virt-post-install-network-config.adoc#virt-post-install-network-config[Network configuration]:
+* Network configuration:
 
 ifndef::openshift-rosa,openshift-dedicated,openshift-rosa-hcp[]
 ** Installing the Kubernetes NMState and SR-IOV Operators
@@ -32,9 +32,16 @@ ifdef::openshift-rosa,openshift-dedicated,openshift-rosa-hcp[]
 ** Enabling the creation of load balancer services by using the {product-title} web console
 endif::openshift-rosa,openshift-dedicated,openshift-rosa-hcp[]
 
-* xref:../../virt/post_installation_configuration/virt-post-install-storage-config.adoc#virt-post-install-storage-config[Storage configuration]:
+* Storage configuration:
 ** Defining a default storage class for the Container Storage Interface (CSI)
 ** Configuring local storage by using the Hostpath Provisioner (HPP)
 
 // * Users
 // * Alerts and notifications
+
+[role="_additional-resources"]
+[id="additional-resources_{context}"]
+== Additional resources
+* xref:../../virt/post_installation_configuration/virt-node-placement-virt-components.adoc#virt-node-placement-virt-components[Specifying nodes for {VirtProductName} components]
+* xref:../../virt/post_installation_configuration/virt-post-install-network-config.adoc#virt-post-install-network-config[Postinstallation network configuration]
+* xref:../../virt/post_installation_configuration/virt-post-install-storage-config.adoc#virt-post-install-storage-config[Postinstallation storage configuration]