chore(core): bump gitlab-ai-provider to 6.19.0 - #53352

Issue for this PR

Closes #53343

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

This is the v2 counterpart of #53345. It bumps the pinned gitlab-ai-provider in packages/core from 6.18.0 to 6.19.0. bun.lock changes only in that pin and the resolved package entry.

6.19.0 adds the duo-chat-sonnet-5-5, duo-workflow-sonnet-5-5 and duo-chat-gpt-6-1-sol mappings. The bundled models.dev snapshot on v2 already lists duo-chat-sonnet-5-5 and duo-chat-gpt-6-1-sol, so they show up in the GitLab picker. Until this bump, agenticChat() rejects them with Unknown model ID. The GitLab plugin doesn't hardcode any model ids, and the release's only source change is src/model-mappings.ts, so no source changes were needed.

How did you verify your code works?

• bun install: packages/core resolves gitlab-ai-provider 6.19.0 from npm, and the installed dist/ contains the new model ids.
• bun typecheck in packages/core passes.
• bun test test/plugin/provider-gitlab.test.ts gives 15 pass, 0 fail.
• packages/core: bun test gives 5599 pass, 1 fail. The failure is Core test environment > isolates global home and XDG roots, which fails the same way on unmodified v2 and is unrelated to this bump.

Screenshots / recordings

Not a UI change.

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR