Optimize version comparison hot paths

[andrew]

Replace regexp- and split-based SemVer, RubyGems, and NuGet comparison with allocation-free scanners. Avoid redundant interval comparisons and regexp parsing for VERS URIs and constraints.

Add benchmarks for scheme comparison, parsing, validation, and highest-satisfying selection, plus randomized parity coverage for scanner behavior.

[Copilot]

Pull request overview

Optimizes version parsing and comparison hot paths by replacing regex/split-based logic with allocation-free scanners across SemVer, RubyGems, and NuGet, and adds parity tests/benchmarks to validate the new scanners.

Changes:

• Replaced SemVer matching/comparison and NuGet prerelease/numeric parsing with scanner-based, low-allocation implementations.
• Replaced VERS URI and constraint operator regex parsing with prefix/index scans.
• Added property-based parity tests and additional benchmarks; tightened interval containment edge coverage.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
version.go	Switches SemVer detection/parsing in ParseVersion and SemVer fast path in CompareVersions to scanner-based parsing.
schemes.go	Implements allocation-free SemVer scanner/prerelease comparison and RubyGems segment scanning (replacing regex/split).
schemes_test.go	Adds randomized parity tests ensuring scanner behavior matches the legacy regex/regexp behavior; adds NuGet edge cases.
pypi.go	Reuses qualifierPre constant in PEP 440 pre-tag mapping.
parser.go	Replaces vers: URI regex parsing with prefix + slash scan and adds newline guard for constraints.
parser_test.go	Adds test coverage for missing separator and newline-in-constraints VERS URI cases.
interval.go	Removes redundant early returns in containsCmp and relies on bound checks for correctness.
interval_test.go	Adds coverage for equal exclusive bounds containment behavior.
ecosystem_extra.go	Uses qualifierPre constant for Gentoo suffix rank handling.
constraint.go	Replaces operator regex with a small scanner (constraintOperator).
bench_test.go	Adds benchmarks for scheme comparison, constraint parsing, cached parsing, validation, and highest-satisfying selection.

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