maint(gitlab): bump gitlab-ai-provider to 6.16.0

[vglafirov]

Issue for this PR

Closes #50741

Type of change

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

What does this PR do?

Bumps the pinned gitlab-ai-provider dependency in packages/core on dev from 6.15.0 to 6.16.0 (the current latest on npm), and updates bun.lock accordingly. This is the only place the package is declared.

6.16.0 adds the duo-chat-opus-5-5 / duo-workflow-opus-5-5 model mappings for Claude Opus 5.5. No source changes were needed — the type surface we consume from packages/core/src/plugin/provider/gitlab.ts (VERSION and the dynamic createGitLab export) is unchanged, so this is a drop-in upgrade.

How did you verify your code works?

• bun install from the repo root — lockfile resolves to 6.16.0.
• bun typecheck in packages/core — passes with no errors.
• Confirmed packages/core/node_modules/gitlab-ai-provider/package.json resolves to 6.16.0 from the npm registry (not a local file: link).

Screenshots / recordings

Not a UI change.

Checklist

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

[github-actions]

Hey! Your PR title maint(gitlab): bump gitlab-ai-provider to 6.16.0 doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Potential duplicate found:

• PR chore: bump gitlab-ai-provider to 6.16.0 #50318: chore: bump gitlab-ai-provider to 6.16.0
  • chore: bump gitlab-ai-provider to 6.16.0 #50318

This appears to be addressing the same dependency bump to 6.16.0. Both PRs are targeting the same gitlab-ai-provider version update. You may want to verify if PR #50318 is already merged, closed, or still open to determine if PR #50742 is redundant.