Share VersionCheck and Registrator helper actions

[mtfishman]

Summary

• Move shared version-bump, registry-route, and release-history logic into a version-helpers composite action used by VersionCheck and Registrator.
• Move General and local registry dispatch into a route-keyed register-version composite action, reducing duplicate route-specific workflow blocks.
• Add focused Julia tests for bump validation, route detection, suffix-free release lookup, and strip-suffix breaking-release metadata.
• Run CheckCompatBounds on draft PRs by default so workflow canaries exercise that check unless callers explicitly opt out.

Validation

• pre-commit run --all-files
• itpkgfmt .
• actionlint .github/workflows/VersionCheck.yml .github/workflows/Registrator.yml .github/workflows/CheckCompatBounds.yml
• git diff --check
• Julia helper tests via include(".github/actions/version-helpers/test/runtests.jl")
• Canary PR in ITensorTestPackage.jl passed VersionCheck, CheckCompatBounds, docs, tests, integration, CodeQL, and Codecov.