fix: prevent extensions recreation by stabilizing suggestion config dependencies

The root cause of broken autocompletion was that suggestion configs were
being extracted via .find() outside useMemo, creating new object references
on every render. These unstable references were then used as dependencies
for the extensions useMemo, causing TipTap extensions to be recreated on
every single render. This destroyed the suggestion system's internal state
including popup visibility and search results.

Changes:
- Move .find() calls inside the extensions useMemo
- Replace individual config dependencies with stable 'suggestions' array
- Extensions now only recreate when suggestions actually change (rare)

This matches React best practices: avoid computing values outside useMemo
when those values are used as dependencies, as they create unstable
references that defeat memoization.

The issue was NOT with TipTap's async handling (my first fix was wrong),
but with React's dependency tracking and object reference stability.

src/components/editor/NostrEditor.tsx

@@ -543,13 +543,13 @@ export const NostrEditor = forwardRef<NostrEditorHandle, NostrEditorProps>(
 
     handleSubmitRef.current = handleSubmit;
 
-    // Find suggestion configs
-    const mentionConfig = suggestions.find((s) => s.char === "@");
-    const emojiConfig = suggestions.find((s) => s.char === ":");
-    const slashConfig = suggestions.find((s) => s.char === "/");
-
     // Build extensions array
     const extensions = useMemo(() => {
+      // Find suggestion configs inside useMemo to avoid recreating extensions on every render
+      const mentionConfig = suggestions.find((s) => s.char === "@");
+      const emojiConfig = suggestions.find((s) => s.char === ":");
+      const slashConfig = suggestions.find((s) => s.char === "/");
+
       const isMobile = "ontouchstart" in window || navigator.maxTouchPoints > 0;
 
       // Custom extension for keyboard shortcuts
@@ -711,14 +711,7 @@ export const NostrEditor = forwardRef<NostrEditorHandle, NostrEditorProps>(
       }
 
       return exts;
-    }, [
-      submitBehavior,
-      placeholder,
-      blobPreview,
-      mentionConfig,
-      emojiConfig,
-      slashConfig,
-    ]);
+    }, [submitBehavior, placeholder, blobPreview, suggestions]);
 
     const editor = useEditor({
       extensions,