## Task: Shape upload state indicators on track rows

### Context

Cloud upload v1 shipped (2026-03-18): single file upload via toolbar + right-click context menu on local tracks. The v1 `UploadService` tracks state globally (idle/uploading/success/error) but there's **no per-track visual indicator** of upload status.

We already have per-track **download** state indicators on track rows (downloaded/downloading/error icons, managed by `DownloadManager` and `Track.downloadState`). The user wants **symmetrical upload indicators** — so a track row shows whether it's been uploaded to the cloud, is currently uploading, or failed.

### What needs shaping

1. **Per-track upload state model**: Currently `UploadService` is fire-and-forget — it doesn't associate uploads with Track objects. We need a way to track "this local Track has been uploaded to cloud" or "is currently uploading". Options:
   - Add `uploadState` to the `Track` SwiftData model (mirrors `downloadState`)
   - Keep it transient (in-memory only, lost on restart)
   - Persist upload history separately

2. **Visual indicators on track rows**: The row already shows download state icons. How should upload state appear?
   - Same position as download indicators? Or opposite side?
   - What icons/colors for: uploading (progress), uploaded (checkmark? cloud?), failed (red)?
   - Should "uploaded" persist after beets reorganizes the file (server-side the track ID changes)?

3. **Interaction between upload and download states**: A track could theoretically be both "downloaded from cloud" AND "uploaded to cloud" (if you download a cloud track, it becomes local, then re-upload). How to handle overlapping states?

4. **Multi-file queue implications**: If we later add batch upload (#1 from pre-brief), per-track state becomes essential for showing queue progress. Shape this with batch in mind.

### Design questions for @designer
- Where on the track row should upload state appear?
- Icon vocabulary: what SF Symbols for uploading/uploaded/failed?
- Does it conflict with the existing download state indicators?
- Color coding: match download state colors or differentiate?

### Existing code to review
- `Sources/Models/Track.swift` — has `downloadState` enum and property
- `Sources/Views/TrackRow.swift` — renders download state indicators
- `Sources/Views/PlaylistView.swift` — context menu with "Upload to Cloud"
- `Sources/Services/UploadService.swift` — current global state, no per-track tracking
- `Sources/Services/DownloadManager.swift` — per-track download state pattern to mirror

### Pre-brief reference
See `briefs/cloud-upload-v2-prebrief.md` for the full list of deferred upload items and suggested grouping.