Single Error Label Masked Three Distinct Failures in Test Harness Reducer

A developer discovered that a test harness reducer was returning the same error label, EXEC_ARGUMENTS_MISMATCH, for three fundamentally different failure conditions across separate test fixtures. The root cause was a single try-catch block that grouped argument parsing errors, value mismatches, and comparator exceptions under one name. The fix involved splitting the parse and compare stages into separate try-catch blocks, each emitting its own distinct failure code: EXEC_ARGUMENTS_INVALID, EXEC_ARGUMENTS_MISMATCH, and EXEC_COMPARATOR_ERROR respectively. After the change, the same three fixtures now return different, accurately descriptive labels depending on which stage actually failed. A contributor described the fix as a rename rather than a redesign, noting the change touched three source files plus associated tests.