Draft: fix(agentic chat): not working outside of project

What does this MR do and why?

This MR fixes the current limitation of Agentic Chat that it can't be used outside of project context. This limitation was originally coming from that Duo Workflow is tightly coupled with project entity. This MR drops the project requirement from Agentic Chat workflow where keeps the project still required for the other workflow definitions.

This is required for the feature parity with Classic Duo Chat which has already cross-project and group-level entity support (e.g. ask question about epic where there are no 1-to-1 relationships with a project). Also, competitors such as Windsurf has cross-project context support by default.

References

To release this feature on production, the following changes need to be merged in this order:

1. GitLab-Rails: gitlab!194821 (closed)
2. Duo Workflow Service: gitlab-org/modelops/applied-ml/code-suggestions/ai-assist!2807 (merged)
3. GitLab-LSP gitlab-org/editor-extensions/gitlab-lsp!1870 (closed)
4. Editor Extension (VSCode): !2693 (closed)

Related to Agentic Chat doesn't work outside of project (G... (gitlab#550324 - closed)

How has this been tested?

• If src/browser or src/common has been modified, please consider interoperability with the Web IDE. See Running the Extension in WebIDE.
• Consider an end-to-end test for significant new features that aren't covered by integration tests.

Screenshots (if appropriate)

What CHANGELOG entry will this MR create?

• fix: Bug fix fixes - a user-facing issue in production - included in changelog
• feature: New feature - a user-facing change which adds functionality - included in changelog
• BREAKING CHANGE: (fix or feature that would cause existing functionality to change) - should bump major version, mentioned in the changelog
• None - other non-user-facing changes