Calls to `.get` on TypeVars bound to TypedDict narrow to `object`

Bug Report

When using dict.get to access specific members of TypeVar entries bound to TypedDict, mypy always narrows the type to object where, without the TypeVar, we expect the union of the underlying type and None.

To Reproduce

from typing import TypedDict, TypeVar

class MyDict(TypedDict):
    my_attributes: list[str]

def take_my_dict(d: MyDict):
    reveal_type(d['my_attributes'])
    reveal_type(d.get('my_attributes'))

MyDictT = TypeVar('MyDictT', bound=MyDict)

def take_my_typevar(d: MyDictT):
    reveal_type(d['my_attributes'])
    reveal_type(d.get('my_attributes'))

Expected Behavior

   main.py:7: note: Revealed type is "builtins.list[builtins.str]"
   main.py:8: note: Revealed type is "Union[builtins.list[builtins.str], None]"
   main.py:13: note: Revealed type is "builtins.list[builtins.str]"
   main.py:14: note: Revealed type is "Union[builtins.list[builtins.str], None]"

Actual Behavior

   main.py:7: note: Revealed type is "builtins.list[builtins.str]"
   main.py:8: note: Revealed type is "Union[builtins.list[builtins.str], None]"
   main.py:13: note: Revealed type is "builtins.list[builtins.str]"
=> main.py:14: note: Revealed type is "builtins.object"

Your Environment

• Mypy version used: 1.8.0
• Mypy command-line flags: n/a
• Mypy configuration options from mypy.ini (and other config files): n/a
• Python version used: 3.12

Start with the main.py reproducer and run mypy against the TypedDict and TypeVar cases, comparing the reveal_type output for .get. Trace the type-checking path for a .get call on a TypeVar bound to TypedDict; done means the TypeVar case reveals Union[list[str], None] rather than object.