ruff check --fix --select F541 . on current main. Pure prefix removals; adjacent-string concatenations keep the f only on interpolating fragments. No string content or live placeholder altered.
Reorganize flat tests/ directory to mirror source code structure (tools/, gateway/, hermes_cli/, integration/). Add 11 new test files covering previously untested modules: registry, patch_parser, fuzzy_match, todo_tool, approval, file_tools, gateway session/config/ delivery, and hermes_cli config/models. Total: 147 unit tests passing, 9 integration tests gated behind pytest marker.