feat: add Pangea AI Guard community integration

[kenany]

Description

Adds a new community integration, Pangea AI Guard, to NeMo Guardrails.

@Pouyanpi

Checklist

• I've read the CONTRIBUTING guidelines.
• I've updated the documentation if applicable.
• I've added tests if applicable.
• @mentions of the person or team responsible for reviewing proposed changes.

[github-actions]

Documentation preview

https://nvidia.github.io/NeMo-Guardrails/review/pr-1300

[Copilot]

Pull Request Overview

This PR adds a new community integration for Pangea AI Guard to NeMo Guardrails, enabling protection against prompt injection attacks, PII detection, toxicity filtering, and other AI safety risks through configurable detection policies.

Key changes include:

• Implementation of Pangea AI Guard integration with input/output rail support
• Configuration options for recipe-based detection policies
• Example configurations for both Colang v1 and v2
• Comprehensive documentation and test coverage

Reviewed Changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
nemoguardrails/library/pangea/actions.py	Core action implementation for Pangea AI Guard API integration
nemoguardrails/rails/llm/config.py	Configuration models for Pangea rail options and settings
nemoguardrails/library/pangea/flows.co	Colang v2 flow definitions for input/output guardrails
nemoguardrails/library/pangea/flows.v1.co	Colang v1 flow definitions for input/output guardrails
tests/test_pangea_ai_guard.py	Unit tests for Pangea AI Guard output functionality
examples/configs/pangea*	Example configurations demonstrating integration usage
docs/user-guides/community/pangea.md	Complete integration documentation and setup guide

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