fix: Remove Modal integration tests from PR workflow

Modal integration tests are too resource-intensive to run on every PR.
They should only run as part of the push/deploy workflow to main.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: anth-volk

.github/workflows/pr.yml

@@ -144,12 +144,3 @@ jobs:
       run: |
         docker compose -f deployment/docker-compose.yml down
 
-  # Deploy to Modal staging and run Modal-specific integration tests
-  test-modal-integration:
-    name: Test Modal integration
-    needs: docker-build
-    uses: ./.github/workflows/modal-deploy.reusable.yml
-    with:
-      environment: beta
-      modal_environment: staging
-    secrets: inherit