Improve SQLModel constructor hover and completion

[ting-hong-shieh]

Summary

• prefer an overridden __init__ signature when a class inherits an unannotated catch-all __new__
• use the same preference for constructor call traces so hover and signature surfaces agree
• add SQLModel-shaped Pydantic regressions for hover and keyword completion

Root cause

SQLModel defines __new__(cls, *args: Any, **kwargs: Any) without a return annotation. For subclasses, Pyrefly combined that inherited catch-all with the synthesized Pydantic __init__; the broader signature then obscured the model fields in IDE surfaces even though constructor diagnostics still checked those fields correctly.

The new preference is intentionally narrow: __new__ must be inherited, unannotated, and gradual, while __init__ must be overridden. Direct construction continues to check both methods.

User impact

SQLModel subclasses now expose their synthesized Pydantic fields in hover and keyword completion instead of only args and kwargs.

Test plan

• cargo test -p pyrefly test::lsp::hover::
• cargo test -p pyrefly test::lsp::completion::
• cargo test -p pyrefly constructor
• python3 test.py --no-test --no-tensor-shapes --no-conformance --no-jsonschema

Fixes #4530

[meta-codesync]

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