- The SSE branch selects a caller-supplied `eventSourceInit.fetch` as-is, so
it bypassed the challenge observer and a first-time legacy SSE
authorization lost the advertised URL the same way. Observing is passive,
so it is applied to that fetch too while the deliberate no-proxy-wrap rule
stays. Covered behaviorally against a 401-serving server.
- Dropped an `as unknown as typeof fetch` from the new integration test
(banned by AGENTS.md, and it erased the signature); the spy is typed as
`typeof fetch` directly. The `as MCPServerConfig` beside it was
unnecessary too.
- The integration test reused a per-pid OAuth storage file. SDK `auth()`
persists the advertised URL in its discovery state, so a rerun could
satisfy discovery from that cache and pass with the plumbing removed —
which would have quietly falsified the regression check. Fresh mkdtemp
per run, removed in teardown.
Adds observer unit tests (challenge reported, body untouched, 403 included,
silent on success).
Signed-off-by: cliffhall <cliff@futurescale.com>