Final (context-sensitive Literal) doesn't support type narrowing

Bug Report

Maybe there's a reason this is not supported, but at a quick look it seems like it should work. When a union of context-sensitive Literals are used, it fails to perform type narrowing, whereas explicit Literals do work.

To Reproduce

from typing import Final, Literal

class TXTRecord:
    type: Final = "TXT"
    text: str = "Foo"

class ARecord:
    type: Final = "A"
    host: str = "192.168.1.1"

record: TXTRecord | ARecord
reveal_type(record.type)
if record.type == "TXT":
    print(record.text)  # error with Final, but not with Literal
else:
    print(record.host)  # error with Final, but not with Literal

Start by running the provided Python reproduction and compare its narrowing behavior with the equivalent explicit Literal case. The work is done when the Final-based union narrows to TXTRecord and ARecord in the two branches without producing the reported attribute errors.