docs(dynamix): use exported $theme directly, don't reassign

Remove $theme = $Dynamix['theme'] pattern since $theme and other
$Dynamix entries are already exported as top-level variables in
.page files. Add note warning against mutating shared variables.

Thanks @Squidly271 in issue #2

Author: mstrhakr

docs/core/dynamix-framework.md

@@ -25,8 +25,11 @@ The `$Dynamix` array contains essential configuration and state information abou
 // Access the Dynamix configuration
 global $Dynamix;
 
-// Example: Check current theme
-$theme = $Dynamix['theme'];
+// Exported variables like $theme are already available in page files
+// and mirror values from $Dynamix.
+if ($theme === 'black') {
+    // dark theme logic
+}
 ?>
 ```
 
@@ -89,9 +92,6 @@ $formattedNumber = number_format($value, 2, $decimal, $thousands);
 
 ```php
 <?
-global $Dynamix;
-
-$theme = $Dynamix['theme'];
 $isDarkTheme = in_array($theme, ['black', 'gray']);
 ?>
 
@@ -110,6 +110,9 @@ $isDarkTheme = in_array($theme, ['black', 'gray']);
 </style>
 ```
 
+{: .note }
+> In `.page` files, variables like `$theme` are already exported. Avoid reassigning or mutating these shared variables.
+
 ### Theme CSS Variables
 
 Unraid themes define CSS variables you can use for consistent styling: