[red-knot] mypy_primer: split installation and execution (#16622)

## Summary

I noticed that the pipeline can succeed if there are problems with tool
installation or dependency resolution. This change makes sure that the
pipeline fails in these cases.

.github/workflows/mypy_primer.yaml

@@ -43,6 +43,10 @@ jobs:
       - name: Install Rust toolchain
         run: rustup show
 
+      - name: Install mypy_primer
+        run: |
+          uv tool install "git+https://github.com/astral-sh/mypy_primer.git@add-red-knot-support"
+
       - name: Run mypy_primer
         shell: bash
         run: |
@@ -58,18 +62,15 @@ jobs:
 
           cd ..
 
-          echo "Running mypy_primer"
-
-          (
-            uvx --verbose --from "git+https://github.com/astral-sh/mypy_primer.git@add-red-knot-support" mypy_primer \
-              --repo ruff \
-              --type-checker knot \
-              --old base_commit \
-              --new "$GITHUB_SHA" \
-              --project-selector '/(mypy_primer|black|pyp|git-revise|zipp|arrow)$' \
-              --output concise \
-              --debug > mypy_primer.diff
-          ) || [ $? -eq 1 ]
+          # Allow the exit code to be 0 or 1, only fail for actual mypy_primer crashes/bugs
+          uvx mypy_primer \
+            --repo ruff \
+            --type-checker knot \
+            --old base_commit \
+            --new "$GITHUB_SHA" \
+            --project-selector '/(mypy_primer|black|pyp|git-revise|zipp|arrow)$' \
+            --output concise \
+            --debug > mypy_primer.diff || [ $? -eq 1 ]
 
           # Output diff with ANSI color codes
           cat mypy_primer.diff