Resolve nested class forward references in annotations

[cakeni]

Summary

Allow postponed and quoted annotations in a class body to resolve a nested class declared later in that same body. The deferred class-body lookup now records whether same-class forward resolution is legal, while ordinary runtime reads keep the existing inherited-only behavior.

Tests cover the future-annotations regression on Python 3.13, both annotations before and after the nested class declaration, and a runtime read that must still report unknown-name.

Fixes #4410

Test Plan

• cargo +stable-x86_64-pc-windows-gnu test -p pyrefly --lib test_nested_class_ -- --nocapture (9 passed)
• python test.py --no-test --no-tensor-shapes --no-conformance --no-jsonschema
• cargo fmt --all -- --check
• git diff --check

[meta-codesync]

This pull request has been imported. If you are a Meta employee, you can view this in D115588128. (Because this pull request was imported automatically, there will not be any future comments.)

[github-actions]

According to mypy_primer, this change doesn't affect type check results on a corpus of open source code. ✅