fix: preserve ranges with no matching versions when simplifying

[jakezwang]

When none of the supplied versions match, simplifyRange returns an empty string, which matches every stable version:

semver.simplifyRange(['1.0.0', '1.1.0'], '^2.0.0') // ''
semver.satisfies('1.0.0', '')                       // true

Preserve the original range when the matching set is empty. Regression tests cover string ranges, Range objects, and the null range <0.0.0-0.

Validation: npm test passes, including 100% coverage, ESLint, and template-oss-check.

References

The simplifyRange contract requires matching the same versions from the supplied list.