Move validator comparisons to validgen-benchmarks

[leocavalcante]

Summary

• Move the ValidGen vs go-playground/validator benchmarks, including the handwritten baseline, to opencodeco/validgen-benchmarks.
• Move TestColorMatchesValidator there too. It was the remaining import of github.com/go-playground/validator/v10, so this module can drop that requirement.
• TestGen writes the comparative suite into that checkout when VALIDGEN_BENCHMARKS_DIR is set. make testgen runs go run . so coverage_test.go is not passed to the generator.

Fixes #44

Test plan

• go test ./internal/... ./types/... ./testgen/
• make endtoendtests
• go mod tidy leaves no direct github.com/go-playground/validator/v10 requirement
• In validgen-benchmarks, make smoke (package tests plus one iteration of each comparison side)
• make testgen VALIDGEN_BENCHMARKS_DIR=... rewrites the comparative files identical to the copies taken from main

[Copilot]

Copilot review overview

🟢 Approval recommended

The benchmark migration, dependency cleanup, generator behavior, and documentation are consistent and complete.

Review effort: Balanced
Findings: None

What changed in this PR

Moves validator comparison benchmarks and compatibility checks to validgen-benchmarks, removing the main module’s validator dependency.

Changes:

• Removes local comparative benchmark suites and templates.
• Adds optional cross-repository benchmark generation via VALIDGEN_BENCHMARKS_DIR.
• Updates dependencies and documentation for the new workflow.

File	Description
types/​color.go	Links the color comparison location.
types/​color_test.go	Replaces dependency-based comparison with local smoke tests.
tests/​cmpbenchtests/​generated_cmp_perf_no_pointer_test.go	Removes generated comparisons.
tests/​bench/​validgen_test.go	Removes local ValidGen benchmark.
tests/​bench/​validator_test.go	Removes validator benchmark.
tests/​bench/​validator__.go	Removes generated benchmark validator.
tests/​bench/​types.go	Removes benchmark models.
tests/​bench/​manual_coding.go	Removes handwritten baseline.
tests/​bench/​manual_coding_test.go	Removes baseline benchmark tests.
testgen/​README.md	Documents external generation.
testgen/​generate_cmp_perf_tests.go	Writes comparisons into the external checkout.
testgen/​cmp_perf_pointer_tests.tpl	Removes relocated pointer template.
testgen/​cmp_perf_no_pointer_tests.tpl	Removes relocated value template.
README.md	Redirects benchmark usage and results.
Makefile	Removes local benchmark targets and updates TestGen.
go.sum	Removes obsolete dependency checksums.
go.mod	Drops validator and promotes x/text.
docs/​internals.md	Documents cross-repository TestGen behavior.
.github/​copilot-instructions.md	Updates contributor benchmark guidance.

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[Copilot]

Copilot review overview

🟢 Approval recommended

The migration, generator behavior, dependency cleanup, and documentation are consistent with the stated objective.

Review effort: Balanced
Findings: None