v2.8.18-canary.14

<!-- Release notes generated using configuration in .github/release.yml at v2.8.18-canary.14 -->

What's Changed

Changelog

• fix: Hardening for supporting private GitHub repos in turbo gen workspace --copy by @anthonyshew in https://github.com/vercel/turborepo/pull/12336
• refactor: Wire GroupingLayer into Visitor and migrate task error/warn to turborepo-log by @anthonyshew in https://github.com/vercel/turborepo/pull/12337
• perf: Replace subprocess repo index with in-process gix-index by @anthonyshew in https://github.com/vercel/turborepo/pull/12339

Full Changelog: https://github.com/vercel/turborepo/compare/v2.8.18-canary.13...v2.8.18-canary.14