Clarify prefix usage in App Group documentation

- Remove widget-specific prefix examples that implied different prefixes per process
- Emphasize that limitToInstance: false listens to ALL system UserDefaults notifications
- Clarify that prefix acts as a filter to respond only to intended suiteName changes
- Use better examples showing different App Groups rather than same-group processes
- Update performance considerations to reflect system-wide notification listening

This addresses the misconception that different processes in the same App Group
need different prefixes, when actually they typically share the same prefix
and the prefix serves to isolate different suites.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

Author: fatbobman

README.md

@@ -252,10 +252,10 @@ class Settings {
 // For App Group cross-process synchronization
 @ObservableDefaults(
     suiteName: "group.myapp",
-    prefix: "widget_",
+    prefix: "myapp_",
     limitToInstance: false
 )
-class WidgetSettings {
+class SharedSettings {
     var lastUpdate: Date = Date()
 }
 ```
@@ -624,45 +624,53 @@ Use the `limitToInstance: false` parameter to enable cross-process notifications
 ```swift
 @ObservableDefaults(
     suiteName: "group.com.yourcompany.app",
-    prefix: "widget_",  // IMPORTANT: Use unique prefixes
+    prefix: "myapp_",  // IMPORTANT: Use a unique prefix
     limitToInstance: false  // Enable cross-process notifications
 )
-class WidgetSettings {
+class SharedSettings {
     var lastUpdate: Date = Date()
     var displayCount: Int = 0
 }
 ```
 
-#### Important: Always Use Unique Prefixes
+#### Critical: Always Use a Unique Prefix
 
-When `limitToInstance: false`, the macro receives ALL UserDefaults notifications. Without unique prefixes, your app might react to unrelated UserDefaults changes from other parts of your app or different App Groups.
+When `limitToInstance: false`, the macro listens to ALL UserDefaults change notifications from the entire system, not just your specific suite. This means it will receive notifications from:
+
+- `UserDefaults.standard`
+- Other App Groups (`group.otherapp`)
+- Any other UserDefaults instances in your app
+
+**The prefix acts as a filter** to ensure your class only responds to changes from your intended suiteName:
 
 ```swift
-// Main App
+// App Group suite
 @ObservableDefaults(
     suiteName: "group.myapp",
-    prefix: "main_",
+    prefix: "myapp_",  // Only respond to keys starting with "myapp_"
     limitToInstance: false
 )
-class AppSettings {
-    var userName: String = "User"  // Stored as "main_userName"
+class AppGroupSettings {
+    var sharedData: String = "data"  // Stored as "myapp_sharedData"
 }
 
-// Widget
+// Different App Group suite
 @ObservableDefaults(
-    suiteName: "group.myapp",
-    prefix: "widget_",
+    suiteName: "group.anotherapp",
+    prefix: "anotherapp_",  // Only respond to keys starting with "anotherapp_"
     limitToInstance: false
 )
-class WidgetData {
-    var userName: String = "Widget"  // Stored as "widget_userName"
+class AnotherAppSettings {
+    var sharedData: String = "other"  // Stored as "anotherapp_sharedData"
 }
 ```
 
+Without unique prefixes, your `AppGroupSettings` might incorrectly react to changes from `group.anotherapp` or `UserDefaults.standard`.
+
 #### Performance Considerations
 
-- **Default (`limitToInstance: true`)**: Better performance, only monitors specific instance changes. Use for single-process apps.
-- **Cross-Process (`limitToInstance: false`)**: Necessary for App Groups but receives more notifications. Unique prefixes help filter relevant changes.
+- **Default (`limitToInstance: true`)**: Better performance, only monitors changes from the specific UserDefaults instance. Recommended for single-process apps.
+- **Cross-Process (`limitToInstance: false`)**: Necessary for App Groups but receives ALL system UserDefaults notifications. The prefix is essential to filter only relevant changes from your target suite.
 
 ### General Notes