Fails if runners are on arm64 (?)

Hi,

Using the scan-action against a private ECR, it worked fine while we were producing AMD64 images, but now that we produce buildx arm64 images (index + arm64 image only), it fails. Below an extract from the action log.

Also, our runners are self-hosted, and also run on arm64.

```
Downloading grype v0.97.1 via https://raw.githubusercontent.com/anchore/grype/main/install.sh
sh /home/runner/work/_temp/3e39c01b-3a7e-48ba-879d-76168fc72e48 -d -b /tmp/grype-download-Us0ma7 v0.97.1
[info] checking github for release tag='v0.97.1'

[debug] http_download(url=https://github.com/anchore/grype/releases/v0.97.1)

[info] fetching release script for tag='v0.97.1'

[debug] http_download(url=https://get.anchore.io/grype/v0.97.1/install.sh)

[info] checking github for release tag='v0.97.1'

[debug] http_download(url=https://github.com/anchore/grype/releases/v0.97.1)

[info] using release tag='v0.97.1' version='0.97.1' os='linux' arch='amd64'

[debug] downloading files into /tmp/tmp.xaCkqPySYX

[debug] http_download(url=https://github.com/anchore/grype/releases/download/v0.97.1/grype_0.97.1_checksums.txt)

[debug] http_download(url=https://github.com/anchore/grype/releases/download/v0.97.1/grype_0.97.1_linux_amd64.tar.gz)

[info] installed /tmp/grype-download-Us0ma7/grype

/opt/hostedtoolcache/grype/0.97.1/x64/grype -v -o table --file /home/runner/work/Shift/Shift/grype-results-shift/connector-bloomberg-backend.out --fail-on medium 123456789012.dkr.ecr.eu-central-2.amazonaws.com/shift/connector-bloomberg-backend:axxxxxxc-feat-dependabot-pip-docker-db--d187-9340629e46e8ece39c7d1e5f6c62255d23126d5c
[0000] INFO grype version: 0.97.1

[0000] INFO docker pulling image image=123456789012.dkr.ecr.eu-central-2.amazonaws.com/shift/connector-bloomberg-backend:axxxxxxc-feat-dependabot-pip-docker-db--d187-9340629e46e8ece39c7d1e5f6c62255d23126d5c

[0000] INFO downloading new vulnerability DB

[0002] INFO gathered packages packages=0 time=2.890892375s

[0007] INFO downloaded vulnerability DB time=7.912473676s url=https://grype.anchore.io/databases/v6/vulnerability-db_v6.0.3_2025-08-12T01:31:01Z_1754972022.tar.zst?checksum=sha256%3A08ec6965228cd1cfdcf8fe06b477d0d6a003e0885498bc69b792c649716df402

[0024] INFO installed new vulnerability DB built=2025-08-12T04:13:42Z version=v6.0.3

[0024] INFO loaded DB status=valid time=24.868855915s

[0024] ERROR failed to catalog: errors occurred attempting to resolve '123456789012.dkr.ecr.eu-central-2.amazonaws.com/shift/connector-bloomberg-backend:axxxxxxc-feat-dependabot-pip-docker-db--d187-9340629e46e8ece39c7d1e5f6c62255d23126d5c':
- snap: snap file "123456789012.dkr.ecr.eu-central-2.amazonaws.com/shift/connector-bloomberg-backend:axxxxxxc-feat-dependabot-pip-docker-db--d187-9340629e46e8ece39c7d1e5f6c62255d23126d5c" does not exist
- docker: no matching manifest for linux/amd64 in the manifest list entries
- podman: podman not available: no host address
- containerd: containerd not available: failed to dial "/run/containerd/containerd.sock": connection error: desc = "transport: error while dialing: dial unix /run/containerd/containerd.sock: connect: permission denied"
- oci-registry: failed to get image from registry: no child with platform linux/amd64 in index 123456789012.dkr.ecr.eu-central-2.amazonaws.com/shift/connector-bloomberg-backend:axxxxxxc-feat-dependabot-pip-docker-db--d187-9340629e46e8ece39c7d1e5f6c62255d23126d5c
- snap: no snap found with name '123456789012.dkr.ecr.eu-central-2.amazonaws.com/shift/connector-bloomberg-backend:axxxxxxc-feat-dependabot-pip-docker-db--d187-9340629e46e8ece39c7d1e5f6c62255d23126d5c'
- additionally, the following providers failed with file does not exist: docker-archive, oci-archive, oci-dir, singularity, oci-dir, local-file, local-directory
```

Thank you.

No source file or test is named. Start by tracing the action's Grype installation and invocation shown in the log, then inspect how the requested linux/amd64 platform is selected for the ECR image; done means the action can catalog the arm64-only image on the reported arm64 runner.

Written by the indexing model from the issue text.