Introduce per-page progress events for PDF parsing by adding onPageStarted
hooks throughout the compute worker and core PDF pipeline. Add
compute/worker/src/pdf-progress.ts to encapsulate progress event builders.
Update server logic to emit page start and page parsed events, improving
client feedback during long-running PDF jobs.
Add src/lib/server/compute/abort-like-error.ts and integrate isAbortLikeError
to robustly detect and suppress expected aborts in API event streaming.
Update API route to ignore abort-like errors on worker proxy crash.
Add unit tests for abort-like error detection and PDF progress event
generation. Refactor PDF parse logic to allow empty merged regions without
throwing, ensuring downstream flows remain resilient to edge cases.
These changes improve observability, error handling, and reliability for
document parsing and event streaming.