Summary

Fixes #19858 by preferring the active provider when a requested model can be normalized into one of that provider's native model IDs.

Before this change, ambiguous Claude Sonnet inputs such as claude-sonnet-4.6 or anthropic/claude-sonnet-4.6 could fall through to generic provider detection and get remapped to an aggregator catalog entry instead of staying on the already-active Anthropic provider.

What changed

• normalize the requested model against the current provider before cross-provider detection
• if the normalized ID already belongs to the current provider catalog, keep the provider unchanged and reuse the native ID
• add regression coverage for both:
  • anthropic/claude-sonnet-4.6 while already on anthropic
  • claude-sonnet-4.6 while already on anthropic

Validation

• scripts/run_tests.sh tests/hermes_cli/test_models.py tests/hermes_cli/test_model_switch_variant_tags.py
• direct reproduction check:
  • detect_provider_for_model('anthropic/claude-sonnet-4.6', 'anthropic')
  • detect_provider_for_model('claude-sonnet-4.6', 'anthropic')
  • both now resolve to ('anthropic', 'claude-sonnet-4-6')

Notes

This keeps the existing fallback behavior for true cross-provider switches, but stops same-provider Claude inputs from being hijacked by later OpenRouter-style detection.