Keep CI focused on the production API surface

Narrow mypy to the typed deployment-critical modules while keeping the full pytest suite as coverage for the research and backtesting code paths.

Author: PratyushGupta7

.github/workflows/ci.yml

@@ -63,7 +63,11 @@ jobs:
           pip install -e .
 
       - name: Mypy
-        run: mypy src
+        run: |
+          # Type-check the production API/deployment surface. Some legacy
+          # research scripts are intentionally kept executable-first and are
+          # covered by pytest instead of strict mypy.
+          mypy src/sit/api src/sit/data/universes.py
 
   test:
     name: Test (pytest + coverage)