The initial fit-to-width in the pdf viewer measures container.clientWidth
immediately after showViewer() flips display:flex. Under CI load the reflow
can lag a tick, leaving widthFit >= 1.0 and zoom at 100% when first read,
which intermittently fails the toBeLessThan(100) assertion (~6 failures in
the 30 runs since #583).

Swap the single-shot read for expect.poll, matching the pattern already used
for the post-fullscreen assertion below, then capture inlineZoom for the
subsequent comparison.

A host may interpose a long-running or user-interactive step between the
guest's tools/call and the server's response. Without this, the base
SDK's default request timeout in Protocol.request() fires and the guest
sees -32001 even though the host is still working.

Passing onprogress causes Protocol.request to include _meta.progressToken
in the outgoing request and register a progress handler;
resetTimeoutOnProgress makes incoming notifications/progress reset the
per-request timer. Hosts can then heartbeat during long-running steps.
Callers can still override both.