upload-to-trixie gives confusing error message when uploading binaries along with the source
The upload appears to succeed but the workflow fails with `Unable to find an artifact of category debian:source-package with a relationship of type extends from "Id: 3565911 Category: debian:upload Workspace: 3"`
```
$ dput debusine.debian.net 7zip_25.01+dfsg-1~deb13u2_amd64.changes
Uploading 7zip using debusine to debusine.debian.net (host: debusine.debian.net; directory: /)
running debusine-check-workflow: check debusine workflow for distribution
running checksum: verify checksums before uploading
running suite-mismatch: check the target distribution for common errors
running gpg: check GnuPG signatures before the upload
Not checking GPG signature due to allow_unsigned_uploads being set.
Uploading 7zip-dbgsym_25.01+dfsg-1~deb13u2_amd64.deb
Uploading 7zip-standalone-dbgsym_25.01+dfsg-1~deb13u2_amd64.deb
Uploading 7zip-standalone_25.01+dfsg-1~deb13u2_amd64.deb
Uploading 7zip_25.01+dfsg-1~deb13u2_amd64.buildinfo
Uploading 7zip_25.01+dfsg-1~deb13u2_amd64.deb
Uploading 7zip_25.01+dfsg-1~deb13u2_amd64.changes
Uploading .../7zip_25.01+dfsg-1~deb13u2_amd64.buildinfo to https://debusine.debian.net/api/1.0/artifact/3565911/files/7zip_25.01%2Bdfsg-1~deb13u2_amd64.buildinfo/
Uploading .../7zip_25.01+dfsg-1~deb13u2_amd64.changes to https://debusine.debian.net/api/1.0/artifact/3565911/files/7zip_25.01%2Bdfsg-1~deb13u2_amd64.changes/
Uploading .../7zip_25.01+dfsg-1~deb13u2_amd64.deb to https://debusine.debian.net/api/1.0/artifact/3565911/files/7zip_25.01%2Bdfsg-1~deb13u2_amd64.deb/
Uploading .../7zip-dbgsym_25.01+dfsg-1~deb13u2_amd64.deb to https://debusine.debian.net/api/1.0/artifact/3565911/files/7zip-dbgsym_25.01%2Bdfsg-1~deb13u2_amd64.deb/
Uploading .../7zip-standalone_25.01+dfsg-1~deb13u2_amd64.deb to https://debusine.debian.net/api/1.0/artifact/3565911/files/7zip-standalone_25.01%2Bdfsg-1~deb13u2_amd64.deb/
Uploading .../7zip-standalone-dbgsym_25.01+dfsg-1~deb13u2_amd64.deb to https://debusine.debian.net/api/1.0/artifact/3565911/files/7zip-standalone-dbgsym_25.01%2Bdfsg-1~deb13u2_amd64.deb/
Created artifact: https://debusine.debian.net/debian/developers/artifact/3565911/
running debusine-create-workflow: create a debusine workflow
Failed to create workflow upload-to-trixie: Cannot create workflow: Unable to find an artifact of category debian:source-package with a relationship of type extends from "Id: 3565911 Category: debian:upload Workspace: 3"
```
issue