[ty] Add support for dict(...) calls in typed dict contexts (#22113)
## Summary
fixes https://github.com/astral-sh/ty/issues/2127
- handle `dict(...)` calls in TypedDict context with bidirectional
inference
- validate keys/values using the existing TypedDict constructor implem
- mdtest: add 1 positive test, 1 negative test for invalid coverage
## Test Plan
```sh
cargo clippy --workspace --all-targets --all-features -- -D warnings # Rust linting
cargo test # Rust testing
uvx pre-commit run --all-files --show-diff-on-failure # Rust and Python formatting, Markdown and Python linting, etc.
```
fully green