fix: stale model catalog — missing Claude 4.5/4.6, deprecated GPT-3.5 default

[stackbilt-admin]

CodeBeast Audit Finding — P1 HIGH

Severity: P1 — High
Category: Correctness / Model Currency
Files: providers/anthropic.ts, providers/openai.ts, index.ts

Problem

The model catalog is stale and contains errors:

Missing Models

• Claude Haiku 4.5 (claude-haiku-4-5-20251001)
• Claude Sonnet 4.5 (claude-sonnet-4-5-20250514)
• Claude Sonnet 4.6 (claude-sonnet-4-6-20250618)
• Claude Opus 4.6 (claude-opus-4-6-20250618)

Incorrect Model IDs

• claude-sonnet-3.7-20241120 is wrong — correct ID is claude-3-7-sonnet-20250219

Stale Pricing

• Claude 4 models have costs marked // Estimated - actual pricing TBD
• These models have had published pricing for months

Deprecated Default

• openai.ts:278: request.model || 'gpt-3.5-turbo' — GPT-3.5 Turbo is deprecated
• Should default to gpt-4o-mini (cheaper, better, not deprecated)

Missing from MODELS Constants

• index.ts MODELS object and MODEL_RECOMMENDATIONS need updating to include current-gen models

Fix

1. Add Claude 4.5/4.6 model entries with correct pricing
2. Fix claude-sonnet-3.7 model ID
3. Update Claude 4 pricing from published rates
4. Change OpenAI default from gpt-3.5-turbo to gpt-4o-mini
5. Update MODELS and MODEL_RECOMMENDATIONS in index.ts

🤖 Filed by CodeBeast audit