Add module filter E2E matrix

[Will-thom]

Summary

• add an end-to-end module filter matrix using the compiled CLI binary
• verify module filtering by artifactId and module path with the nested module fixture
• cover no-match behavior in text and JSON
• assert JSON findingCount and findings reflect the filtered view
• document module filter E2E coverage in the testing guide

Validation

• go test ./cmd/prmaven -run TestCLIModuleFilterMatrix -v
• .github/scripts/check-public-metadata.sh
• go test ./...
• git diff --check

Closes #76

[github-actions]

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