Bug: incorrect parsing of path parameters with nested routers

[ulbwa]

Describe the bug
When using nested routers with path parameters, the values are parsed incorrectly. Specifically, when passing a valid enum value in the subject, only the last character of the path parameter is taken.

How to reproduce

from enum import StrEnum
from typing import Annotated, Any

from faststream import FastStream, Path
from faststream.nats import NatsBroker, NatsRouter


class MyEnum(StrEnum):
    FIRST = "first"
    SECOND = "second"
    THIRD = "third"


broker = NatsBroker()
root_router = NatsRouter(prefix="root_router.")
nested_router = NatsRouter()


@nested_router.subscriber("{my_enum}.nested_router")
async def do_nothing(message: Any, my_enum: Annotated[MyEnum, Path()]): ...


root_router.include_router(nested_router)
broker.include_router(nested_router)
app = FastStream(broker)


@app.after_startup
async def run():
    await broker.publish("", f"root_router.{MyEnum.THIRD}.nested_router")

Expected behavior
The my_enum path parameter should be correctly parsed, matching the full enum value (e.g., “third”).

Observed behavior

pydantic_core._pydantic_core.ValidationError: 1 validation error for do_nothing
my_enum
  Input should be 'first', 'second' or 'third' [type=enum, input_value='d', input_type=str]
    For further information visit https://errors.pydantic.dev/2.8/v/enum