fix: improvements

frontend/src/app/canvas/useCanvasGraph.ts

@@ -3,7 +3,7 @@
  * with initial graph from recollection storage (or example). Save is explicit via save().
  */
 
-import { useCallback, useMemo, useRef, useState } from 'react'
+import { useCallback, useEffect, useMemo, useRef, useState } from 'react'
 import { useGraphStateWithHistory } from '@/hooks/useGraphStateWithHistory'
 import { getInitialGraph } from '@/app/canvas/canvasGraphUtils'
 import { saveGraphToStorage, RECOLLECTION_VERSION } from '@/app/recollections/state/recollectionGraphStorage'
@@ -59,5 +59,16 @@ export function useCanvasGraph(recollectionId: string | undefined): UseCanvasGra
     }, SAVING_DISPLAY_MS)
   }, [recollectionId])
 
+  // Auto-save after 5 seconds of inactivity when there are unsaved changes.
+  // Prevents data loss if the user closes the tab without pressing Ctrl+S.
+  const AUTO_SAVE_DELAY_MS = 5000
+  const saveRef = useRef(save)
+  saveRef.current = save
+  useEffect(() => {
+    if (!isDirty || !recollectionId) return
+    const timer = setTimeout(() => saveRef.current(), AUTO_SAVE_DELAY_MS)
+    return () => clearTimeout(timer)
+  }, [isDirty, recollectionId, currentSerialized])
+
   return { ...result, save, saveStatus }
 }