Fix bad merge: lastPrefetchArgs -> prefetchCache, prefetchCacheSize

The merge of #2002 (prefetch-offload-to-mount) on top of #2004
(expand-prefetch-cache) left two call sites referencing the removed
lastPrefetchArgs variable:

  - PrefetchVerb.cs line 234: the hydration-fallback path added by
    #2002 passed lastPrefetchArgs instead of the prefetchCache +
    prefetchCacheSize parameters added by #2004.

  - InProcessMount.cs HandlePrefetchBlobsRequest: the mount-side
    prefetch handler added by #2002 passed lastPrefetchArgs instead
    of explicit null + 0 (mount-side prefetch is a one-shot download
    with no noop cache).

Assisted-by: Claude Opus 4.6
Signed-off-by: Tyrie Vella <tyrielv@gmail.com>

Author: tyrielv

GVFS/GVFS.Mount/InProcessMount.cs

@@ -1123,7 +1123,8 @@ private void HandlePrefetchBlobsRequest(NamedPipeMessages.Message message, Named
                         objectRequestor,
                         request.Files,
                         request.Folders,
-                        lastPrefetchArgs,
+                        prefetchCache: null,
+                        maxCacheSize: 0,
                         chunkSize: 4000,
                         searchThreadCount: maxThreads,
                         downloadThreadCount: downloadThreads,

GVFS/GVFS/CommandLine/PrefetchVerb.cs

@@ -231,7 +231,7 @@ protected override void Execute(GVFSEnlistment enlistment)
                                     cacheServerFromConfig,
                                     out objectRequestor,
                                     out resolvedCacheServer);
-                                this.PrefetchBlobs(tracer, enlistment, headCommitId, filesList, foldersList, lastPrefetchArgs, objectRequestor, resolvedCacheServer);
+                                this.PrefetchBlobs(tracer, enlistment, headCommitId, filesList, foldersList, prefetchCache, prefetchCacheSize, objectRequestor, resolvedCacheServer);
                             }
                             else
                             {