perf: prevent FPS drops during navigation in FluxNoteView

- Narrow backlinks watcher from entire store to store.files only,
  reducing trigger count from ~8 to 2 per navigation
- Defer computation start by 300ms so it runs after the 250ms view
  transition animation completes
- Yield to the browser between each file iteration using
  scheduler.yield() (with setTimeout fallback) to avoid blocking frames

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/hooks/useComputeBacklinks.hook.ts

@@ -14,10 +14,19 @@ import { confirmMessage } from "@/utils/notif"
 
 const isMarkdown = (filename?: string) => filename?.endsWith(".md") ?? false
 
+const yieldToMain = () =>
+  "scheduler" in globalThis
+    ? (globalThis as unknown as { scheduler: { yield: () => Promise<void> } }).scheduler.yield()
+    : new Promise<void>((r) => setTimeout(r, 0))
+
 export const useComputeBacklinks = () => {
   const store = useUserRepoStore()
 
-  watch(store, async () => {
+  watch(
+    () => store.files,
+    async () => {
+      await new Promise<void>((r) => setTimeout(r, 300))
+
       if (!store.userSettings?.backlink) {
         return
       }
@@ -27,6 +36,8 @@ export const useComputeBacklinks = () => {
       const backlinks: Map<string, Backlink[]> = new Map()
 
       for (const file of store.files) {
+        await yieldToMain()
+
         if (!isMarkdown(file.path) || !file.sha) {
           continue
         }
@@ -102,5 +113,6 @@ export const useComputeBacklinks = () => {
         await data.update(backlinkNote)
         backlinkEventBus.emit({ fileSha: sha })
       }
-  })
+    }
+  )
 }