Final grep: 0 send_result in active code. 3 historical refs in
error_handling.md (intentional, in the 'Historical deprecation' note).
Test verification: 100/101 tests pass in the 26 files renamed by this
track. 1 pre-existing failure in test_headless_service.py due to
missing credentials.toml (verified against origin/master baseline
where it also fails - unrelated to the rename).
