fix(resolver): exclude prereleases from stable version ranges - #11

Summary

Stable version ranges could select a prerelease outside the requested range. With tags v1.0.0, v1.1.0, v1.2.0-rc.1, v2.0.0-beta.1, --from 1.0.0 resolved to 2.0.0-beta.1 and --up-to-next-minor-from 1.1.0 resolved to 1.2.0-rc.1, because 2.0.0-beta.1 < 2.0.0 under SemVer precedence.

Range membership is now separate from ordering (SemanticVersion.isInRange(from:to:)) and applies to --from, --up-to-next-minor-from and explicit --from … --to ranges:

• a stable candidate is eligible when lower <= candidate < upper;
• a prerelease candidate is also eligible only when a bound that itself has prerelease identifiers shares the candidate's major.minor.patch.

Stable-only ranges therefore never select a prerelease; when no eligible tag exists, resolution fails with the existing "tag in range" error. Explicit prerelease ranges (for example 0.1.0-alpha.1..<0.1.0), prerelease upper bounds, exact matches and SemVer ordering are unchanged.

Validation

• swift build — pass
• swift test — 113 tests in 17 suites pass
• xcrun swift-format lint --configuration .swift-format --recursive Package.swift Sources Tests — exit 0, no warnings in changed files
• git diff --check — clean
• Manual check with an isolated HOME: --from 1.0.0 selects 1.1.0; --up-to-next-minor-from 1.1.0 selects 1.1.0; --from 1.2.0 with only 1.2.0-rc.1/2.0.0-beta.1 above fails with tag in range 1.2.0..<2.0.0.

Resolves #6