feat(opencode): AI SDK v6 Migration - v5 Compat Layer

[catrielmuller]

Issue for this PR

Closes #6300

Related: #13527 @rekram1-node

Type of change

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

What does this PR do?

• Upgrade AI SDK from v5 to v6
• Upgrade @ai-sdk/* providers to their latest versions
• Migrated deprecated @gitlab/gitlab-ai-provider to gitlab-ai-provider (v5)
• Updated @openrouter/ai-sdk-provider to 2.2.3
• Remove patch for @openrouter/ai-sdk-provider
• New Compatibility Shim (packages/opencode/src/provider/shim.ts) that provides a compatibility layer so that older v5-style provider plugins continue to work with the new v6 SDK APIs
• Adapt to v6 types.

Local Nix Dev Improvements

• Added playwright drivers
• Added git env variables on test/preload.ts

How did you verify your code works?

• bun tun typecheck
• bun run test

opencode:test:  1273 pass
opencode:test:  5 skip
opencode:test:  0 fail
opencode:test:  2696 expect() calls
opencode:test: Ran 1278 tests across 86 files. [51.31s]

Checklist

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

[github-actions]

Hey! Your PR title AI SDK v6 Migration - v5 Compat Layer 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]

Thanks for updating your PR! It now meets our contributing guidelines. 👍