Switch README diagrams to vertical layout

infra-run/ansible/inventory/group_vars/README.md

@@ -5,7 +5,7 @@ This folder is reserved for shared Ansible variables applied to inventory groups
 ## Diagram
 
 ```mermaid
-flowchart LR
+flowchart TD
   A["group_vars"] --> B["Environment defaults"]
   A --> C["Role parameters"]
   A --> D["Shared operational values"]

infra-run/ansible/inventory/host_vars/README.md

@@ -5,7 +5,7 @@ This folder is intended for host-specific Ansible variables. It complements `gro
 ## Diagram
 
 ```mermaid
-flowchart LR
+flowchart TD
   A["host_vars"] --> B["Host A overrides"]
   A --> C["Host B overrides"]
   A --> D["Per-node secrets or tuning"]

infra-run/ansible/tests/README.md

@@ -5,7 +5,7 @@ This directory is reserved for validation of Ansible content. It represents the
 ## Diagram
 
 ```mermaid
-flowchart LR
+flowchart TD
   A["tests"] --> B["Syntax checks"]
   A --> C["Molecule or scenario tests"]
   A --> D["Post-run validation"]