[ty] Preserve checks for recursive descriptor setter types

[charliermarsh]

Summary

This PR fixes a stack overflow when checking a protocol's writable member whose descriptor setter accepts a recursive type. For example, checking the assignment below previously aborted the process instead of reporting an invalid assignment:

from __future__ import annotations

from typing import Protocol

class Recursive[T](Protocol):
    next: Recursive[list[T]]

class Descriptor:
    def __init__(self, getter: object) -> None: ...
    def __get__(self, instance: object, owner: type | None = None) -> int:
        return 1

    def __set__[U](self, instance: object, value: Recursive[int]) -> None: ...

class HasValue(Protocol):
    @Descriptor
    def value(self) -> int: ...

def update(obj: HasValue) -> None:
    obj.value = 1  # Invalid: the setter requires Recursive[int].

The setter's unused U triggers a search to determine whether the accepted value type depends on that type parameter. The existing search follows next through Recursive[int], Recursive[list[int]], Recursive[list[list[int]]], and so on. Its recursion guard remembers exact types, so these changing specializations never repeat and the search overflows the stack. Removing U avoids the search and the crash.

We replace that general type search with a dependency check that recognizes repeated definitions and inspects the arguments of recursive references without repeatedly expanding their bodies. Here, it establishes that the setter accepts Recursive[int] independently of U, so we can report the invalid assignment normally. The same fix covers recursive TypedDicts and type aliases, while retaining checks for assignments and protocol compatibility.

[astral-sh-bot]

Typing conformance results

No changes detected ✅

Current numbers

The percentage of diagnostics emitted that were expected errors held steady at 98.24%. The percentage of expected errors that received a diagnostic held steady at 98.24%. The number of fully passing files held steady at 134/146.

[astral-sh-bot]

Memory usage report

Memory usage unchanged ✅

[astral-sh-bot]

ecosystem-analyzer results

No diagnostic changes detected ✅

Large timing changes:

Project	Old Time	New Time	Change
django-test-migrations	0.10s	0.05s	-53%

Flaky changes detected. This PR summary excludes flaky changes; see the HTML report for details.

Full report with detailed diff (timing results)