fix: support adaptive thinking type and fix beta header handling

[jhfnetboy]

Summary

• Add ThinkingConfigAdaptive to the Anthropic request validation schema to support Claude 4-6+ models that use thinking: {"type": "adaptive"}
• Fix anthropic-beta header handling: use minimal required tags (claude-code-20250219, oauth-2025-04-20) and block CLI fallback headers from overwriting them

Problem

1. Sending thinking: {"type": "adaptive"} (required for Claude 4-6 models) was rejected with a 422 validation error because the schema only accepted enabled/disabled
2. The fallback CLI headers overwrote the anthropic-beta header with tags (e.g. fine-grained-tool-streaming-2025-05-14) that caused "The long context beta is not yet available for this subscription" errors

Changed files

• ccproxy/llms/models/anthropic.py — Add ThinkingConfigAdaptive class and include it in ThinkingConfig union type
• ccproxy/plugins/claude_api/adapter.py — Use minimal beta tags for OAuth auth, block CLI headers from overwriting anthropic-beta

Test results

Claude Sonnet 4-6 (no thinking):

{"model":"claude-sonnet-4-6","id":"msg_01SQMx3YzCznFH7NvUxJuMSQ",
 "content":[{"type":"text","text":"Hello! I'm Claude, made by Anthropic."}],
 "stop_reason":"end_turn"}

Claude Opus 4-6 (adaptive thinking):

{"model":"claude-opus-4-6","id":"msg_01EvK23seKBqAuRDmsXR2S3Y",
 "content":[
   {"type":"thinking","thinking":"The user is asking what model I am."},
   {"type":"text","text":"Hi! I'm Claude, made by Anthropic."}
 ],"stop_reason":"end_turn",
 "usage":{"input_tokens":16,"output_tokens":64}}

Test plan

• curl with thinking: {"type": "adaptive"} returns successful response
• curl without thinking parameter still works
• OAuth authentication works with minimal beta tags
• E2E: EvoScientist CLI -> ccproxy -> Claude Sonnet 4-6
• E2E: ccproxy -> Claude Opus 4-6 with adaptive thinking

Generated with Claude Code