Adjust encoded paths so filenames resolve as a basename properly when downloading with things like wget.

ui/src/server/catchAllPath.ts

@@ -0,0 +1,19 @@
+/**
+ * Turn a `[...param]` catch-all route param into the requested filesystem path.
+ *
+ * Next.js hands catch-all params over as an array of URL segments with the
+ * percent-encoding of each segment already decoded, so both URL forms map to
+ * the same path:
+ *   /api/files/%2Fmnt%2Fout%2Fjob%2Ffile.safetensors        (legacy: one segment)
+ *   /api/files/%2Fmnt%2Fout%2Fjob/file.safetensors          (folder / filename)
+ * The second form gives downloaders (wget, browsers) the real filename as the
+ * last URL segment. Windows paths arrive with their backslashes intact inside
+ * a segment (`C:\out\job` + `/` + `file.safetensors`); path.resolve on the
+ * caller side normalizes the mixed separators.
+ *
+ * Mirrors the per-segment decode in cron/fileServer.ts serveFile().
+ */
+export const catchAllToFilePath = (param: string | string[] | undefined): string => {
+  if (param === undefined) return '';
+  return (Array.isArray(param) ? param : [param]).join('/');
+};