carlobeltrame / ecamp3 / 30161185352
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carlobeltrame 
Fix client PDF hang in Firefox by decoding PNGs synchronously

With the react-pdf upgrade (@react-pdf/pdfkit 4.1.0 -> 5.1.1), client-side
PDF generation started hanging forever at 99% in Firefox: after all pages
render, toBlob() never resolves and the worker never returns the blob.

Root cause: pdfkit 5.x switched its PNG decoder from @react-pdf/png-js@3 to
upstream png-js@2. png-js@2's browser build decodes PNGs via fflate's async
unzlib(data, cb), which spawns a Web Worker (Blob URL) per call. Our PDF
render already runs inside a web worker, so every PNG decode spawns a NESTED
web worker. Firefox delivers nested-worker messages unreliably under CPU
load, so some decode callbacks never fire. The affected image XObjects (the
Twemoji emoji PNGs that react-pdf embeds for emoji in the camp text) then
never get .end() called, so document._waiting never reaches 0, push(null)
is never emitted, and the PDF stream never finishes.

This was observed as a flaky, deterministic-point hang: only in Firefox,
only when rendering in the worker, only with enough emoji-bearing content,
and only under high CPU load (busy CI runner or a loaded local machine).

Fix: patch png-js to decode synchronously with unzlibSync. We are already
off the main thread, so a synchronous inflate is appropriate and removes the
nested workers entirely. Verified: 0 nested workers spawned and 0 hangs
across many runs under 24-28 concurrent CPU hogs, with document compression
left enabled. This makes the other attempted band-aids (disabling
compression, reducing CI DB_CPU_LIMIT, test retries, warm-up render)
unnecessary.

Also re-enable the clientPrint e2e test in Firefox, which the fix makes pass.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015hKARMY81YEh8znEzRsfqw
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