fix(content): refresh installed ZIMs when a download completes to prune ghost entries

The Content Explorer remote list already filters out installed ZIMs client-side
(flatData excludes localNames), but the installed-files query has
refetchOnWindowFocus disabled and was never invalidated on download completion.
So when a ZIM finished downloading it dropped off the active-downloads list
(isDownloading -> false) while localFiles stayed stale (isPresent -> false),
letting the just-installed ZIM reappear as a ghost entry until the page remounted.

Add an effect that invalidates the ['zim-files'] query whenever a job drops off
the polled downloads list, so the completed install is picked up and pruned.

Fix originally diagnosed by @johno10661 in #771; reimplemented focused onto
current dev (the accumulated-page/filter groundwork already landed via #731).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

admin/inertia/pages/settings/zim/remote-explorer.tsx

@@ -175,6 +175,26 @@ export default function ZimRemoteExplorer() {
   }, [data, downloads, localFiles])
   const hasMore = useMemo(() => data?.pages[data.pages.length - 1]?.has_more || false, [data])
 
+  // When a ZIM download drops off the polled downloads list it has completed (or been
+  // cancelled). The installed-files query (refetchOnWindowFocus is off) won't otherwise
+  // refresh, so a just-installed ZIM stays absent from `localFiles` and reappears in the
+  // accumulated remote pages as a ghost entry. Refresh it so the item is pruned.
+  const prevDownloadKeysRef = useRef<Set<string>>(new Set())
+  useEffect(() => {
+    const currentKeys = new Set((downloads ?? []).map((d) => d.jobId))
+    let anyRemoved = false
+    for (const key of prevDownloadKeysRef.current) {
+      if (!currentKeys.has(key)) {
+        anyRemoved = true
+        break
+      }
+    }
+    prevDownloadKeysRef.current = currentKeys
+    if (anyRemoved) {
+      queryClient.invalidateQueries({ queryKey: [ZIM_FILES_KEY] })
+    }
+  }, [downloads, queryClient])
+
   const fetchOnBottomReached = useCallback(
     (parentRef?: HTMLDivElement | null) => {
       if (parentRef) {