fix: exclude unshared prereleases from range intersections

[ryanchou1994]

intersects('>1.0.0 <2.0.0', '^2.0.0-0') currently returns true, although no version satisfies both ranges with the default prerelease rules. With includePrerelease: true, 2.0.0-0 is a valid intersection and the result should remain true.

This adds a check after the existing comparator-set intersection succeeds. If both sets do not opt into a common prerelease tuple, their intersection must contain a stable version. Check the least possible stable version against each original set separately, preserving each set's prerelease permissions. This also covers empty gaps between adjacent stable versions and numeric-component rollover.

Related to #345 and its requested includePrerelease: false case. The change is limited to Range.intersects; it does not change version ordering, the existing shared-prerelease path, or address every known intersection defect.

Validation:

• New regression tests fail against the original code and pass with this change, including both argument orders, loose mode, OR ranges, option handling and unchanged parsed comparators.
• Full tests, lint and postlint pass on macOS and Linux: 51 test files and 100% coverage in all four measures. Linux used --jobs=2 for its two-CPU allocation.
• Node 10.0.0 and 10.24.1 each pass 874 additional entry-point/fixture assertions.

The extra check has a measurable cost: a five-round Linux microbenchmark measured public calls at 1.04–1.38× baseline. The smallest prebuilt-Range case was 9.9→31.1 ms per 100,000 calls (about 0.21 µs extra per call). No cache or tooling changes are included.

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