[docs] Template moulding in docs/platform and index improvement (#3663)

docs/templates/quickstart_template.mdx

@@ -43,13 +43,13 @@ estimatedTime: "[~X minutes]"
   [Optional: cross-link to OSS or platform alternative if applicable. Delete if unused.]
 </Tip>
 
-<!-- Optional: delete if not needed -->
+{/* Optional: delete if not needed */}
 ```mermaid
 graph LR
-  A[Install] --> B[Configure keys]
-  B --> C[Add memory]
-  C --> D[Search]
-  D --> E[Delete]
+  A[Install] */} B[Configure keys]
+  B */} C[Add memory]
+  C */} D[Search]
+  D */} E[Delete]
 ```
 
 ## Install dependencies
@@ -212,7 +212,7 @@ await memory.deleteAll({ userId: "alex" });
 - `[Error message]` → `[One-line fix or link to troubleshooting guide]`
 - `[Second error]` → `[How to resolve]`
 
-<!-- DEBUG: verify CTA targets -->
+{/* DEBUG: verify CTA targets */}
 
 <CardGroup cols={2}>
   <Card