Add unit tests for branch family/suite allowlist resolver

[simonbeaudoin0935]

Summary

Add automated unit-test coverage for scripts/resolve_branch_family_suite.sh after the branch/suite validation hardening from #41.

Related: #41
Parent tracking: #15

Scope

• Add script-level tests for resolver success/failure behavior.
• Validate explicit suite allowlist by family.
• Validate expected failure for unsupported suites (for example debian/qcom-next).
• Validate alias inputs accepted by Debian family (latest, unstable).
• Validate ref normalization (refs/heads/*, refs/remotes/*, origin/*).

Acceptance Criteria

• Tests cover valid and invalid refs for both Debian and Ubuntu families.
• Tests assert exit code semantics for parse/family failure vs unsupported suite.
• CI job executes these resolver unit tests on pull requests.