Cannot infer type argument with TypeVarTuple and Callback protocol

To Reproduce

# mypy: enable-incomplete-feature=NewGenericSyntax
from collections.abc import Callable
from typing import Protocol

class ActionType(Protocol):
    def __call__(self, var: str, context: int = 2) -> None: ...

class Job[*_Ts]:
    def __init__(self, target: Callable[[*_Ts], None]) -> None:
        self.target = target

def run_job[*_Ts](job: Job[*_Ts], *args: *_Ts) -> None: ...

def a1(action: ActionType) -> None:
    job = Job(action)
    run_job(job, "Hello")  # -> error

Actual Behavior

error: Cannot infer type argument 1 of "run_job"  [misc]

Expected Behavior
No error. Mypy should be able to tell that context has a default value and is thus optional. It already works from pure Callables (without the intermediate generic class).

def run_job_2[*_Ts](action: Callable[[*_Ts], None], *args: *_Ts) -> None: ...

def a2(action: ActionType) -> None:
    run_job_2(action, "Hello")  # works fine

Your Environment

• Mypy version used: mypy 1.11.0+dev.177c8ee7b8166b3dcf89c034a676ef5818edbc38 (compiled: no) (current master)
• Mypy command-line flags: --enable-incomplete-feature=NewGenericSyntax (the bug exists with the old generic syntax as well)
• Python version used: 3.12

Inizia con il reproducer e confronta il percorso run_job che fallisce con l’esempio funzionante run_job_2 usando Python 3.12 e il flag NewGenericSyntax. Traccia l’inferenza dei tipi per TypeVarTuple attraverso Job e il callback ActionType; il lavoro è completato quando il primo esempio inferisce i propri argomenti senza errori e il comportamento esistente rimane intatto.