Fix missing staging tree link in UI

[bjester]

Summary

Description of the change(s) you made

• Updates toolbar to pass along #extension slot content to Vuetify's component to fix missing link to the staging tree
• Updates logging of sync exceptions to report stack trace, helpful within celery workers
• Updates yarn run celery to run with --concurrency=1 instead of the default matching the quantity of CPUs available

Screenshots (if applicable)

---

Reviewer guidance

How can a reviewer test these changes?

1. Have Studio running locally at http://localhost:8080
2. Use ricecooker to create a cheffed channel:

CONTENTWORKSHOP_URL=http://localhost:8080 python tests/test_chef_integration.py

3. Open the channel in your local Studio
4. Verify you see the same as the screenshot

References

Observed in reviewing #3997

Comments

---

Contributor's Checklist

PR process:

• If this is an important user-facing change, PR or related issue the CHANGELOG label been added to this PR. Note: items with this label will be added to the CHANGELOG at a later time

Studio-specifc:

• All user-facing strings are translated properly
• The notranslate class been added to elements that shouldn't be translated by Google Chrome's automatic translation feature (e.g. icons, user-generated text)
• All UI components are LTR and RTL compliant
• Views are organized into pages, components, and layouts directories as described in the docs
• Users' storage used is recalculated properly on any changes to main tree files
• If there new ways this uses user data that needs to be factored into our Privacy Policy, it has been noted.

Testing:

• Code is clean and well-commented
• Contributor has fully tested the PR manually
• If there are any front-end changes, before/after screenshots are included
• Critical user journeys are covered by Gherkin stories
• Any new interactions have been added to the QA Sheet
• Critical and brittle code paths are covered by unit tests

---

Reviewer's Checklist

This section is for reviewers to fill out.

• Automated test coverage is satisfactory
• PR is fully functional
• PR has been tested for accessibility regressions
• External dependency files were updated if necessary (yarn and pip)
• Documentation is updated
• Contributor is in AUTHORS.md

[vkWeb]

@bjester sir I ran the manual verification steps and the result matched the screenshot! 🚀 A really useful fix!

This is good to merge, there's just a small curiosity that I've commented.

[ozer550]

I also tested this manually and it's working as expected! great to have the link in UI itself.

[LianaHarris360]

Everything looks good to me as well!