`ReturnType<typeof of>` resolves against the zero-argument overload, so the
stub only accepted `Observable<never>` and SPOOL-001 could not hand it the
`of('ok')` it needs. tsc -p tsconfig.tests.json broke on it, which sank the
server preflight job and with it every coverage job that needs it.
The chat images never reached a test: committing them to storage, taking them
back out when a later one fails, and dropping them again when the reply target
turns out to be gone. The interceptor that removes the spool when a request
dies before the handler had none either, and it sits in a domain pinned at 99%
function coverage. Both filters are pinned too, including the disguised
extensions that were the point of changing them.
Maurice