Trace reader: read zip entries on demand instead of up front #498

Part of #494.

Problem

The reader unpacks every entry of a trace zip up front and builds the whole player payload, every screenshot included, before anything renders. Memory and load time grow with the trace.

How others do it

Playwright's trace viewer reads only the zip's central directory when a trace opens, then unpacks individual entries when the UI asks for them (a snapshot, a screenshot, a resource), inside a service worker. Vibium's player instead refuses archives past fixed caps (128 MB zip, 512 MB unpacked for Playwright-format traces).

Proposal

Restructure the reader so it indexes the archive first and reads screenshots and other resources on demand. This is the larger follow-up to the Web Worker sub-issue.