Add claims domain and README for TauBench

[Risper8]

Added insurance claims domain and domain README for TauBench.

[Risper8]

This PR adds a new Insurance Claims domain to TauBench.

Key contributions

• Introduces a structured claims environment with policies, claims, users, and fraud handling
• Defines a strict tool-usage and confirmation protocol aligned with MT-1 evaluation requirements
• Adds a domain-specific policy (policy.md) and environment setup
• Supports claim reporting, document verification, approvals/rejections, payments, and human escalation
• Fully compatible with TauBench’s infrastructure

Motivation

This domain is designed to benchmark AI agent reliability in regulated, high-stakes workflows where:

• Explicit user confirmation is required before state-changing actions
• Tool sequencing and compliance are critical
• Errors have real-world financial and legal implications

Testing

• Executed simulations to validate environment setup and agent-tool interaction.

Feedback and suggestions are welcome.