[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

crates/ty_python_semantic/src/types/infer/builder.rs

@@ -8448,6 +8448,43 @@ impl<'db, 'ast> TypeInferenceBuilder<'db, 'ast> {
             arguments,
         } = call_expression;
 
+        // Fast-path dict(...) in TypedDict context: infer keyword values against fields,
+        // then validate and return the TypedDict type.
+        if let Some(tcx) = tcx.annotation
+            && let Some(typed_dict) = tcx
+                .filter_union(self.db(), Type::is_typed_dict)
+                .as_typed_dict()
+            && callable_type
+                .as_class_literal()
+                .is_some_and(|class_literal| class_literal.is_known(self.db(), KnownClass::Dict))
+            && arguments.args.is_empty()
+            && arguments
+                .keywords
+                .iter()
+                .all(|keyword| keyword.arg.is_some())
+        {
+            let items = typed_dict.items(self.db());
+            for keyword in &arguments.keywords {
+                if let Some(arg_name) = &keyword.arg {
+                    let value_tcx = items
+                        .get(arg_name.id.as_str())
+                        .map(|field| TypeContext::new(Some(field.declared_ty)))
+                        .unwrap_or_default();
+                    self.infer_expression(&keyword.value, value_tcx);
+                }
+            }
+
+            validate_typed_dict_constructor(
+                &self.context,
+                typed_dict,
+                arguments,
+                func.as_ref().into(),
+                |expr| self.expression_type(expr),
+            );
+
+            return Type::TypedDict(typed_dict);
+        }
+
         // We don't call `Type::try_call`, because we want to perform type inference on the
         // arguments after matching them to parameters, but before checking that the argument types
         // are assignable to any parameter annotations.