fix: 9 test assertions mismatched with codegen output

[noahgift]

Summary

9 tests in decy-codegen fail because assertions expect per-macro error messages but production code returns a generic message.

Five-Whys Root Cause

1. Why CI failing? — 9 test assertions don't match production code output
2. Why don't they match? — Tests expect "WEXITSTATUS requires status arg" but gen_call_status_macro() returns "/* macro requires status arg */"
3. Why wrong expectations? — Tests were generated for anticipated behavior that was never implemented (shared helper uses one generic error string)
4. Why not caught before merge? — Tests committed without running against actual production code (test-last)
5. Why not fixed already? — Local fixes exist in working tree but were never committed/pushed

Failing Tests

• class_codegen_tests::test_generate_class_simple_fields
• codegen_coverage_tests::expr_w{exitstatus,ifexited,ifsignaled,termsig}_no_args
• expr_codegen_deep2_tests::w{exitstatus,ifexited,ifsignaled,termsig}_no_args_fallback

Fix

Align test assertions with actual production output. Zero production code changes needed.

🤖 Generated with Claude Code