fix: use server response filename in WebcamCapture serialization (#10220)

## Summary
- WebcamCapture's `serializeValue` was ignoring the `/upload/image`
response and returning the original timestamp-based filename
(`webcam/${timestamp}.png [temp]`)
- This breaks content-addressed storage backends (e.g. Comfy Cloud)
where the server returns a different (hash-based) filename, causing
`ImageDownloadError` at inference time
- Now reads `data.name` and `data.subfolder` from the upload response,
matching the pattern already used by `useNodeImageUpload` and
`useMaskEditorSaver`
- No behavioral change for local ComfyUI — the server already returns
the same filename, it was just being ignored

## Test plan
- [x] WebcamCapture node captures and uploads an image successfully on
local ComfyUI
- [x] WebcamCapture node works correctly on Comfy Cloud (no
`ImageDownloadError`)
- [ ] Duplicate filename edge case: upload two captures with same
timestamp — server-renamed file is used correctly

🤖 Generated with [Claude Code](https://claude.com/claude-code)

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10220-fix-use-server-response-filename-in-WebcamCapture-serialization-3266d73d3650818aa9bdff8d27586180)
by [Unito](https://www.unito.io)

---------

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/extensions/core/webcamCapture.ts

@@ -142,7 +142,10 @@ app.registerExtension({
         useToastStore().addAlert(err)
         throw new Error(err)
       }
-      return `webcam/${name} [temp]`
+      const data = await resp.json()
+      const serverName = data.name ?? name
+      const subfolder = data.subfolder ?? 'webcam'
+      return `${subfolder}/${serverName} [temp]`
     }
 
     // @ts-expect-error fixme ts strict error