fix(@uppy/transloadit): show processing UI when restoring an assembly

When Golden Retriever restores a Transloadit assembly after a page
refresh, the UI was not updated to reflect that the assembly was still
being processed. This caused the Upload button to appear and files to
look like they were ready to upload again, even though the assembly was
already running in the background.

Fix by setting `allowNewUpload: false` and emitting `postprocess-progress`
for each file when restoring an in-progress assembly, so the Dashboard
shows the encoding indicator. When the assembly eventually completes via
the AssemblyWatcher, `allowNewUpload` is reset to `true`.

Fixes #6017

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

Author: Your Name

packages/@uppy/transloadit/src/index.ts

@@ -451,6 +451,10 @@ export default class Transloadit<
         this.completedFiles[file.id] = true
         this.uppy.emit('postprocess-complete', file)
       })
+      // Allow new uploads now that this assembly is complete.
+      // This is especially important when restoring an assembly after a page
+      // refresh, where allowNewUpload is set to false to prevent re-uploading.
+      this.uppy.setState({ allowNewUpload: true })
     })
 
     watcher.on('assembly-error', (id: string, error: Error) => {
@@ -738,6 +742,23 @@ export default class Transloadit<
     this.restored = (async () => {
       const files = restoreState()
       restoreAssemblies(Object.keys(files))
+
+      // If the assembly is still in progress, update the UI to reflect that.
+      // This prevents the Upload button from being shown and shows the
+      // processing indicator for each file.
+      if (previousAssembly.ok !== 'ASSEMBLY_COMPLETED') {
+        this.uppy.setState({ allowNewUpload: false })
+        Object.values(files).forEach(({ id: fileId }) => {
+          const file = this.uppy.getFile(fileId)
+          if (file) {
+            this.uppy.emit('postprocess-progress', file, {
+              mode: 'indeterminate',
+              message: this.i18n('encoding'),
+            })
+          }
+        })
+      }
+
       await updateAssembly()
       this.restored = null
     })()