Deploy workflow isn't deploying anymore

[gadenbuie]

e.g. https://github.com/rstudio/shinycoreci/actions/runs/12269013682

with failures like

Error : Unhandled Exception: child_task=1487876928 child_task_status=failed: Error parsing manifest: Unknown repository for package source: https://posit-dev-shinycoreci.r-universe.dev/

and

Error : Unhandled Exception: child_task=1487876823 child_task_status=failed: Error building image: Error fetching htmltools (0.5.8.9000) source. <CRANPackageSource repo='https://packagemanager.posit.co/cran/latest'> unable to satisfy package: htmltools (0.5.8.900