feat(suse): add support for openSUSE MicroOS and Leap Micro detection

[RajeshRajendiran]

Description

Adds OS detection for openSUSE MicroOS (rolling release, Tumbleweed-based) and openSUSE Leap Micro (versioned, Leap-based) via their /etc/os-release ID values (opensuse-microos and opensuse-leap-micro).

As noted in the issue, exact vulnerability-advisory matching isn't feasible yet for either OS — MicroOS is versioned by build timestamp rather than a real release number, and no advisory data source currently covers either OS's versioning scheme. Per the issue's suggested compromise, this PR is scoped to detection only: users get correct OS family/name in package listings and SBOM output, and can pass --distro <family>/<version> to force vulnerability matching against a supported family/version if they want it.

Changes:

• pkg/fanal/types/const.go: new OpenSUSEMicroOS/OpenSUSELeapMicro constants, wired into PurlNamespace() and OSTypes
• pkg/fanal/analyzer/os/release/release.go: detect the two new ID values
• pkg/purl/purl.go: map both to the rpm PURL type (same family as the other openSUSE/SUSE variants), so SBOM PURLs come out correct
• New test fixtures + test cases mirroring the existing Tumbleweed/SLE Micro patterns
• Docs (docs/guide/coverage/os/index.md, suse.md) updated with the new supported OSes and a note on the vulnerability-matching limitation

/etc/os-release ID values were not present anywhere in this repo, so they were cross-checked against two independent external sources (chef/ohai's platform-detection test fixtures and k0sctl's openSUSE detection code) rather than assumed.

Deliberately out of scope: pkg/detector/ospkg/detect.go / suse.go are untouched. Wiring up real vulnerability matching depends on trivy-db gaining a data source for these OSes first (currently it has none for MicroOS and only partial, disconnected plumbing for Leap Micro) — that's a separate PR against that repo.

Related issues

• Close feat(opensuse): add MicroOS and Leap Micro support #8409

Checklist

• I've read the guidelines for contributing to this repository.
• I've followed the conventions in the PR title.
• I've added tests that prove my fix is effective or that my feature works.
• I've updated the documentation with the relevant information (if needed).
• I've added usage information (if the PR introduces new options) — N/A, no new options introduced.
• I've included a "before" and "after" example to the description (if the PR is a user interface change) — N/A, not a UI change.

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