Add -Wconversion to debug builds and track in cleanliness CI

Adds -Wconversion to the GNU debug compiler flags in CMakeLists.txt.
This catches implicit type coercions (e.g. integer = real truncation)
at compile time.

Adds a Conversion Warnings Diff step and count to cleanliness.yml,
following the same delta-from-master pattern as the existing checks.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: sbryngelson

.github/workflows/cleanliness.yml

@@ -86,6 +86,12 @@ jobs:
               grep -F 'Wmaybe-uninitialized' master.txt > mMaybe.txt
               diff prMaybe.txt mMaybe.txt
 
+          - name: Conversion Warnings Diff
+            continue-on-error: true
+            run: |
+              grep -F 'Wconversion' pr.txt > prConversion.txt
+              grep -F 'Wconversion' master.txt > mConversion.txt
+              diff prConversion.txt mConversion.txt
 
           - name: Everything Diff
             continue-on-error: true
@@ -106,12 +112,14 @@ jobs:
               pr_argument=$(grep -c -F 'Wunused-dummy-argument' pr.txt)
               pr_value=$(grep -c -F 'Wunused-value' pr.txt)
               pr_uninit=$(grep -c -F 'Wmaybe-uninitialized' pr.txt)
+              pr_conversion=$(grep -c -F 'Wconversion' pr.txt)
               pr_everything=$(grep -c '\-W' pr.txt)
 
               master_variable=$(grep -c -F 'Wunused-variable' master.txt)
               master_argument=$(grep -c -F 'Wunused-dummy-argument' master.txt)
               master_value=$(grep -c -F 'Wunused-value' master.txt)
               master_uninit=$(grep -c -F 'Wmaybe-uninitialized' master.txt)
+              master_conversion=$(grep -c -F 'Wconversion' master.txt)
               master_everything=$(grep -c '\-W' master.txt  )    
 
               echo "pr_everything=$pr_everything" >> $GITHUB_ENV
@@ -124,6 +132,7 @@ jobs:
               echo "Unused Dummy Argument: $pr_argument, Difference: $((pr_argument - master_argument))"
               echo "Unused Value: $pr_value, Difference: $((pr_value - master_value))"
               echo "Maybe Uninitialized: $pr_uninit, Difference: $((pr_uninit - master_uninit))"
+              echo "Conversion: $pr_conversion, Difference: $((pr_conversion - master_conversion))"
               echo "Everything: $pr_everything, Difference: $((pr_everything - master_everything))"
           
 

CMakeLists.txt

@@ -150,6 +150,7 @@ if (CMAKE_Fortran_COMPILER_ID STREQUAL "GNU")
             -fsignaling-nans
             -finit-real=snan
             -finit-integer=-99999999
+            -Wconversion
             -Wintrinsic-shadow
             -Wunderflow
             -Wrealloc-lhs