Copilot review (#2287): scoping the stored-CIMD check to the incoming issuer
alone mislabels the SDK's own CIMD write for a second authorization server.
SEP-2352 keys registrations per AS, so the first binding promotes the unkeyed
CIMD entry into issuer A's slot and clears the fallback;
`ensureCimdClientRegistration` then early-returns on its ctx-less read, and the
save under issuer B finds nothing recorded for B.
Check the issuer slot and then the server's active registration, so a second
issuer stays CIMD while a `client_id` the AS minted itself still falls through
to `dcr`. Covered by two tests driving a real `OAuthStorageBase` through the
A → B sequence, since the behaviour under test is how storage promotes and
clears slots rather than anything a mock would express.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Lmj6X2epWpPE7ScdSKQmtA
Signed-off-by: cliffhall <cliff@futurescale.com>