4850c187ea
This fixes cycle panics in several ecosystem projects (moved to `good.txt` in a following PR https://github.com/astral-sh/ruff/pull/17834 because our mypy-primer job doesn't handle it well if we move projects to `good.txt` in the same PR that fixes `ty` to handle them), as well as in the minimal case in the added mdtest. It also fixes a number of panicking fuzzer seeds. It doesn't appear to cause any regression in any ecosystem project or any fuzzer seed.
Markdown files within the mdtest/ subdirectory are tests of type inference and type checking;
executed by the tests/mdtest.rs integration test.
See crates/ty_test/README.md for documentation of this test format.