bug: Recover from MuPDF panic

[iwilltry42]

@cjellick found two files, that, when ingested together (concurrency > 1), trigger a panic in MuPDF. They're attached to this issue. More details in Slack: https://acorn-io.slack.com/archives/C07FZ46QA2J/p1728496324209799

Since they're OK to process sequentially, one workaround would be to

1. recover from panics arising from MuPDF
2. Retry loading the panicking document after a certain time to make sure the conflicting other file was processed in the meantime

CORAL_SafeguardCoralReefs_PerviousPavingOptions.pdf CORAL_SafeguardCoralReefs_RainGardens.pdf