Select classifier models by session provider

[georgesleen]

Context

autoMode.classifierModel is one fixed model. A user who switches the session between providers, such as OpenAI Codex and Anthropic, must either classify through the other provider or manually rewrite and reload the config. The fixed model can also require credentials for a provider that the current session is not using.

No open or closed issue or pull request proposes provider-aware classifier selection.

Desired outcome

Allow user-owned auto-mode settings to select a classifier from the current session model's provider:

{
  "autoMode": {
    "classifierModel": "fallback/model",
    "classifierModelByProvider": {
      "anthropic": "anthropic/claude-haiku-4-5",
      "openai-codex": "openai-codex/gpt-5.6-luna"
    }
  }
}

• Resolve the mapping for every classifier call so an in-session model switch takes effect without a reload.
• Prefer the provider-specific entry, then classifierModel, then the current session model.
• Merge maps across global, project-local, and inline settings; higher-precedence settings replace only named providers.
• Keep /automode model as the editor for the scalar fallback.
• Report the resolved classifier in /automode status and model-visible status inspection.
• Preserve existing behavior when the map is absent.