Impl

Implement the work the user points at: a spec, one or more tickets, or a description.

1. Read the spec and tickets, then design.md, asking the user for its path if they have not given it. It records the chosen implementation direction and the conventions to follow, each with an evidence path. Treat its decisions as settled, and raise any that the code contradicts with the user.
2. Use $tdd where possible, at the seams the spec agreed on.
3. Run typechecking and single test files as you go, and the full test suite once at the end.
4. Run $code-review on the work and fix what it finds.
5. Commit to the current branch.