Updates the terminology and configuration for the intermediate policy tier
from "Project" to "Workspace" to better align with the Gemini CLI ecosystem.
Key changes:
- Renamed `PROJECT_POLICY_TIER` to `WORKSPACE_POLICY_TIER`.
- Renamed `getProjectPoliciesDir` to `getWorkspacePoliciesDir`.
- Updated integrity scope from `project` to `workspace`.
- Updated UI dialogs and documentation.
- Renamed related test files.