feat: modernize Anthropic manifold

[jfbloom22]

Summary

Modernizes the Anthropic manifold around Anthropic’s current Messages API and Open WebUI native tool-calling flow.

• Use async HTTP requests with retries, timeouts, and actionable error handling.
• Support streaming and non-streaming tool-use loops, including OpenAI-style tool-history translation.
• Add capability-aware adaptive/manual thinking configuration and prompt-caching controls.
• Add regression coverage for payload construction, tool execution, history translation, and thinking output.

Validation

• python3 -m unittest discover -s tests -v
• python3 -m py_compile functions/pipes/anthropic/main.py
• git diff --check