✨ Add effect persistence with localStorage

Store and restore the last selected effect across browser sessions

- Save selected effect ID to localStorage when switching effects
- Check localStorage for saved effect during initialization
- Maintain URL parameter priority over saved preference
- Fall back to first effect if neither URL nor saved effect exists

This allows users to return to their previously selected effect
when reopening the development environment.

Author: hyperb1iss

src/dev/engine/preact-engine.ts

@@ -129,9 +129,11 @@ export class PreactDevEngine {
             throw new Error('Canvas element with ID "exCanvas" not found')
         }
 
-        // Get the effect ID from URL or use the first effect
+        // Get the effect ID from URL, localStorage, or use the first effect
         const urlParams = new URLSearchParams(window.location.search)
-        const effectId = urlParams.get('effect') || effects[0].id
+        const urlEffect = urlParams.get('effect')
+        const savedEffect = localStorage.getItem('lastSelectedEffect')
+        const effectId = urlEffect || savedEffect || effects[0].id
 
         // Set basic names for effects to ensure they're visible in UI
         for (const effect of effects as AppEffect[]) {
@@ -229,6 +231,9 @@ export class PreactDevEngine {
             return
         }
 
+        // Save the selected effect to localStorage
+        localStorage.setItem('lastSelectedEffect', effectId)
+
         // Update current effect reference
         this.currentEffect = effect