Add Arize Phoenix Python SDK documentation

[LakshmiN5]

Summary

Add comprehensive Arize Phoenix Python SDK documentation for LLM observability, tracing, and evaluation.

Changes

• Add content/arize/docs/phoenix/python/DOC.md
• Comprehensive documentation covering:
  • Installation and environment setup
  • Project registration and tracing
  • Framework instrumentation (OpenAI, LangChain, CrewAI, Anthropic, etc.)
  • Evaluation workflows with LLM-as-a-judge
  • Common mistakes section (prevents agent hallucinations)
  • Critical Phoenix vs Arize AX distinction

What

Adds curated documentation for the Arize Phoenix Python SDK to help coding agents correctly implement LLM observability.

Content structure:

• Follows <author>/docs/<name>/<language>/DOC.md pattern
• Location: content/arize/docs/phoenix/python/DOC.md
• 311 lines (under 500 line guideline)
• Proper YAML frontmatter with all required fields

Why

Problem this solves:

1. Agent API Confusion: Agents frequently confuse Arize Phoenix with Arize AX (different products, incompatible APIs)
2. Import Hallucinations: Wrong imports (arize.otel vs phoenix.otel), wrong env vars
3. Missing Curated Docs: Phoenix lacks agent-friendly documentation in Context Hub
4. Integration Errors: Improper instrumentation order, framework-specific setup issues

This documentation provides working examples and a "Common Mistakes" section to prevent these issues.

Testing

Content Quality:

• Follows Context Hub content guide structure
• Proper YAML frontmatter (name, description, languages, versions, revision, updated-on, source, tags)
• Under 500 lines (311 lines)
• LLM-friendly formatting with clear sections
• Practical code examples, not just API signatures
• Progressive disclosure approach
• Code examples verified against Phoenix 6.0.0

Build & Tests:

• node cli/bin/chub build content/ --validate-only - PASSED (1554 docs, 6 skills, 0 warnings)
• npm test - ALL 231 TESTS PASSED (20 test files)

Notes

closes issue no 176

Related Resources:

• Official docs: https://arize.com/docs/phoenix
• GitHub: https://github.com/Arize-ai/phoenix
• PyPI: https://pypi.org/project/arize-phoenix/