chore: defer the gateway /v1/files endpoints in the coverage manifest

The gateway added a Files API that no SDK shell wraps yet; defer those five
endpoints under [excluded] so the endpoint-coverage drift gate passes on this
regenerated core. Wrapping the Files API is tracked separately.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: njbrake

sdk-endpoints.txt

@@ -60,3 +60,9 @@ POST /v1/audio/speech          # binary, not yet wrapped
 POST /v1/audio/transcriptions  # binary, not yet wrapped
 POST /v1/images/generations    # binary, not yet wrapped
 GET /v1/models/{model_id}      # redundant, list_models covers discovery
+# Files API: added to the gateway spec, not yet wrapped by any SDK shell.
+POST /v1/files                       # not yet wrapped
+GET /v1/files                        # not yet wrapped
+GET /v1/files/{file_id}              # not yet wrapped
+GET /v1/files/{file_id}/content      # not yet wrapped
+DELETE /v1/files/{file_id}           # not yet wrapped