When hovering, if we find a statement node (like StmtExpr), extract the expression from within it. This allows hover assertions to work on standalone expressions like variable references. Also add a simple working mdtest to demonstrate hover assertions. 🤖 Generated with [Claude Code](https://claude.com/claude-code) Co-Authored-By: Claude <noreply@anthropic.com>
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.