Three findings, all real.
`arrayBuffer()` hands back the decoded entity body, so the rebuilt
response was carrying the upstream `content-encoding` and the
compressed `content-length` — a gzipped metadata document came back as
plain JSON bytes still claiming gzip and the wrong size, visible in the
Network capture. Both headers are deleted now, as `responseWithBody` in
endpointOverrides.ts already did for the same reason.
The "why a race, and not just the signal" rationale described a world
this PR had since changed: the signal does now reach the backend's
outbound fetch. The module doc and three implementation comments are
rewritten to say what the race is actually still for — a fetchFn that
ignores AbortSignal, and a backend that is itself wedged — rather than
a proxy hop that no longer drops it.
The backend cancellation path had only mock-level coverage. A
route-level test drives /api/fetch at an upstream that accepts and never
answers, aborts the browser side, and asserts the upstream observes its
connection closing. Verified by mutation: dropping `signal` from the
route's outbound fetch makes it time out rather than pass.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YFnM6RqB4nXqNysgUYmjmq
Signed-off-by: cliffhall <cliff@futurescale.com>