add credit_breakdown field

[NikhilShahi]

Note

Low Risk
Low risk: adds an optional response field and a new Pydantic model without changing request/behavioral logic; main risk is minor client incompatibility if consumers rely on strict schema serialization.

Overview
Adds support for a new creditBreakdown field on Session, including a new SessionCreditBreakdown Pydantic model to expose total, browser-time, and proxy-data credits used.

Exports SessionCreditBreakdown from hyperbrowser.models and bumps the package version to 0.88.1.

^{Written by Cursor Bugbot for commit 3aee14e. This will update automatically on new commits. Configure here.}