feat: integrate GitLab Duo Agent Platform (DAP) workflow models

[vglafirov]

Problem

OpenCode currently only supports GitLab's agentic chat models (duo-chat-*). GitLab's Duo Agent Platform (DAP) provides server-side agentic workflow models (duo-workflow-*) that drive the agentic loop via the Duo Workflow Service (DWS) WebSocket protocol. These models need to be integrated into OpenCode so users can select and use them alongside existing chat models.

Proposal

• Bump @gitlab/gitlab-ai-provider to 4.0.0 which includes GitLabWorkflowLanguageModel, GitLabModelDiscovery, GitLabModelCache, and isWorkflowModel() APIs
• Add dynamic model discovery that detects the user's GitLab project namespace and queries available DAP models
• Add a model selection picker when multiple workflow models are available, with file-based caching for preferences
• Wire DWS tool execution through OpenCode's existing permission-gated tool system
• Support OAuth instance matching with URL normalization for self-hosted GitLab instances
• Handle finish event token counting for workflow models

Acceptance criteria

• Users can select duo-workflow* models from the model picker
• Model discovery auto-detects available models for the user's namespace
• Selected model preference is cached to disk for fast startup
• DWS tool execution is bridged through OpenCode's tool permission system
• OAuth tokens are correctly matched to the configured GitLab instance
• Model banner correctly shows sub-model name only for workflow models
• All new code uses gitlab- prefix to minimize upstream footprint
• Test coverage for model selection lifecycle, server routes, provider logic, and processor changes

[github-actions]

This issue doesn't fully meet our contributing guidelines.

What needs to be fixed:

• The title should start with [FEATURE]: for feature requests (e.g. [FEATURE]: integrate GitLab Duo Agent Platform (DAP) workflow models)
• The Feature Request template requires a verification checkbox confirming you have searched for existing issues — this appears to be missing

Please edit this issue to address the above within 2 hours, or it will be automatically closed.

If you believe this was flagged incorrectly, please let a maintainer know.

[github-actions]

Thank you for updating the issue! However, it still has a couple of items that need to be addressed before it meets our contributing guidelines:

1. Title format: Feature request titles must start with [FEATURE]:. Please update the title to something like: [FEATURE]: integrate GitLab Duo Agent Platform (DAP) workflow models

2. Verification checkbox: The Feature Request template requires a checkbox confirming you have searched for existing issues to avoid duplicates. Please add it to the issue body, e.g.:
   - [ ] I have searched for existing issues and this is not a duplicate

Please edit the issue to address these points. If you believe this was flagged incorrectly, please let a maintainer know.

[github-actions]

Thank you for updating this issue! However, it still doesn't fully meet the Feature Request template requirements:

1. Title format: The title must start with [FEATURE]:. Please update it from feat: integrate... to [FEATURE]: integrate...
2. Verification checkbox: The Feature Request template requires a verification checkbox (confirming you've searched for existing issues, etc.). This appears to be missing from the issue body.

Please update the issue to address these points and we'll re-review. Thanks!

[github-actions]

This issue still doesn't fully meet our contributing guidelines.

What still needs to be fixed:

• The title must start with [FEATURE]: — please update it to: [FEATURE]: integrate GitLab Duo Agent Platform (DAP) workflow models
• The Feature Request template requires a verification checkbox confirming you have searched for existing issues — this is still missing

Please edit the issue title and body to address the above.

[github-actions]

This issue still doesn't fully meet our contributing guidelines.

What still needs to be fixed:

• The title must start with [FEATURE]: (e.g. [FEATURE]: integrate GitLab Duo Agent Platform (DAP) workflow models)
• The Feature Request template requires a verification checkbox confirming you have searched for existing issues — this is still missing from the issue body

Please edit the issue to address both of these points. Thanks!

[github-actions]

This issue still doesn't meet our contributing guidelines after the recent edit.

What still needs to be fixed:

1. Wrong title format — Feature requests must have a title starting with [FEATURE]:. Please rename to something like: [FEATURE]: integrate GitLab Duo Agent Platform (DAP) workflow models
2. Wrong template used — The issue uses a custom format (Problem / Proposal / Acceptance criteria) instead of the required Feature Request template. Please re-submit using the correct template.
3. Missing verification checkbox — The Feature Request template requires a checkbox confirming you have searched for existing issues before opening this one.

Please edit the issue to use the Feature Request template and address the points above. If you believe this was flagged incorrectly, please let a maintainer know.

[github-actions]

Thank you for updating this issue! Unfortunately, it still doesn't meet our Feature Request template requirements:

1. Title format: The title must start with [FEATURE]:. Please update it from feat: integrate... to [FEATURE]: integrate...
2. Verification checkbox: The Feature Request template requires a verification checkbox (e.g. confirming you've searched for existing issues to avoid duplicates). This is still missing from the issue body.

Please edit the issue to address these two points. If you believe this was flagged incorrectly, please let a maintainer know.

[github-actions]

Thank you for updating the issue content — the Problem and Proposal sections look good. However, two required items are still missing:

1. Title format: Feature request titles must start with [FEATURE]:. The current title (feat: integrate GitLab Duo Agent Platform (DAP) workflow models) needs to be updated to: [FEATURE]: integrate GitLab Duo Agent Platform (DAP) workflow models

2. Verification checkbox: The Feature Request template requires a checkbox confirming you have searched for existing issues to avoid duplicates. Please add a line like:
   - [ ] I have searched for existing issues and this is not a duplicate

Please edit the issue title and body to address these two points. If you believe this was flagged incorrectly, please let a maintainer know.

[github-actions]

This issue still doesn't meet the Feature Request template requirements. Two items remain outstanding:

1. Title format: The title must start with [FEATURE]:. Please change it from feat: integrate... to [FEATURE]: integrate GitLab Duo Agent Platform (DAP) workflow models.

2. Verification checkbox: The Feature Request template requires a checkbox confirming you have searched for existing issues and this is not a duplicate. Please add something like:
   - [ ] I have searched for existing issues and this is not a duplicate

The content of the issue itself is solid — these are the only two things blocking compliance. Please update the title and add the checkbox, and this will be approved.

[github-actions]

This issue has been automatically closed because it was not updated to meet our contributing guidelines within the 2-hour window.

Feel free to open a new issue that follows our issue templates.