Fix for valid tag@digest image references during registry inspection

[Kaniska (v-Kaniska244)]

Summary

Fix OCI reference parsing for references that contain both a tag and a digest as reported in #1307:

mcr.microsoft.com/devcontainers/go:2.3.1-1.27-bookworm@sha256:...

Problem

getRef() previously removed the digest but left the tag attached to the repository resource:

mcr.microsoft.com/devcontainers/go:2.3.1-1.27-bookworm

The resulting path contained :, failed repository path validation, and caused getRef() to return undefined.

Tag-and-digest references are valid OCI references. The digest identifies the exact manifest, while the tag remains useful reference metadata.

Changes

• Detect and extract a tag before parsing a digest.
• Remove the tag from resource and path.
• Preserve the extracted tag in OCIRef.tag.
• Continue using the digest as OCIRef.version.
• Distinguish a tag separator from a colon in a registry port.

For example:

docker.io:8001/example/features/test:1.2.3@sha256:...

is parsed as:

registry: docker.io:8001
resource: docker.io:8001/example/features/test
tag: 1.2.3
digest: sha256:...
version: sha256:...

Test Coverage

Added regression coverage in containerFeaturesOCI.test.ts for:

• An MCR reference containing both a tag and digest.
• A reference containing a registry port, tag, and digest.
• Correct registry, namespace, resource, path, tag, and digest parsing.
• Digest precedence for the resolved version.

Validation

• Focused OCI parser tests pass.
• Full OCI test suite passes with 32 tests.
• Type checking passes.
• ESLint passes.