Feat: Persist all unsaved workflow tabs (#6050)

## Summary

- Keep all drafts in localStorage, mirroring the logic from VSCode.

- Fix a bug where newly created blank workflow tabs would incorrectly
restore as defaultGraph instead of blankGraph after page refresh.

Resolves https://github.com/Comfy-Org/desktop/issues/910, Resolves
https://github.com/Comfy-Org/ComfyUI_frontend/issues/4057, Fixes
https://github.com/Comfy-Org/ComfyUI_frontend/issues/3665

## Changes

### What
- Fix `restoreWorkflowTabsState` to parse and pass workflow data from
drafts when recreating temporary workflows
- Add error handling for invalid draft data with fallback to default
workflow
- Fix E2E test `should not serialize color adjustments in workflow` to
wait for workflow persistence before assertions
- Add proper validation for workflow nodes array in test assertions

### Breaking
- None

### Dependencies
- No new dependencies added

## Review Focus

1. **Workflow restoration**: Verify that blank workflows correctly
restore as blankGraph after page refresh
2. **Error handling**: Check that invalid draft data gracefully falls
back to default workflow
3. **Test coverage**: Ensure E2E test correctly waits for workflow
persistence before checking node properties
4. **Edge cases**: Test with multiple tabs, switching between tabs, and
rapid refresh scenarios

---------

Co-authored-by: Yourz <crazilou@vip.qq.com>

src/locales/en/main.json

@@ -1749,6 +1749,7 @@
     "nothingToQueue": "Nothing to queue",
     "pleaseSelectOutputNodes": "Please select output nodes",
     "failedToQueue": "Failed to queue",
+    "failedToSaveDraft": "Failed to save workflow draft",
     "failedExecutionPathResolution": "Could not resolve path to selected nodes",
     "no3dScene": "No 3D scene to apply texture",
     "failedToApplyTexture": "Failed to apply texture",