Implement Phase 2: Per-project test discovery for multi-project workspaces

[Copilot]

Previously, test discovery ran once per workspace folder. This fails for monorepos with multiple Python projects, where each project has its own configuration (pyproject.toml, pytest.ini, setup.py).

Changes

Project Detection

• Uses environment extension's getPythonProjects() API to detect Python projects
• Queries projects from environment extension when available
• Falls back to workspace root as single project if environment extension not available or no projects found
• Filters projects by workspace to only process projects in current workspace

Controller Architecture

• Changed adapter storage: Map<Uri, WorkspaceTestAdapter> → Map<string, ProjectTestAdapter[]>
• Each workspace maintains multiple project-specific adapters
• createProjectAdapter() instantiates adapters with project root as working directory

Discovery Flow

// Before: single discovery per workspace
workspace → adapter.discoverTests(workspaceUri)

// After: parallel discovery per project
workspace → envExtApi.getPythonProjects() → [project1, project2, ...] 
         → adapter1.discoverTests(project1.uri)
         → adapter2.discoverTests(project2.uri)

Test Execution Routing

• Groups test items by containing project based on file paths
• Routes each group to its project-specific adapter
• Supports cross-project test runs in single execution

Example

For a workspace with structure:

/workspace
  ├── service-a/
  │   ├── pyproject.toml
  │   └── tests/
  └── service-b/
      ├── pytest.ini
      └── tests/

Discovery now runs twice (once per project) with correct working directories, instead of once at workspace root with potentially incorrect configuration.

Backward Compatibility

Single-project workspaces behave identically to before. When environment extension is not available, falls back to treating workspace as single project.

Original prompt

implement what is outlined in this doc as: ### Phase 2: Run Discovery Per Project. we have already done phase 1

Created from VS Code.

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[eleanorjboyd]

@copilot saw your planning and you don't need: Create Project Root Detection. the environments extension handles detection, you just query the env ext api to get the info. Also lets rely on existing file watchers now, since they already exist for the test updating. If you feel they don't cover it add a todo and we can cirlce back

[Copilot]

@copilot saw your planning and you don't need: Create Project Root Detection. the environments extension handles detection, you just query the env ext api to get the info. Also lets rely on existing f...

Updated implementation to use the environment extension API instead of custom project detection:

• Removed projectRootFinder.ts and its tests
• Now calling envExtApi.getPythonProjects() to get project information
• Falls back to workspace root when env extension not available or no projects found
• Existing file watchers retained - they already handle test updates

Commit: 24d8613