Summary

Completes the Worker trait migration to model-aware methods, building on the ModelCard/ModelType foundation.

Key changes:

• Worker trait methods now require a model_id parameter for model-specific config lookup
• Model configuration (tokenizer_path, reasoning_parser, tool_parser, chat_template) is now stored in ModelCard objects instead of the labels HashMap
• Worker registration creates proper ModelCard objects from config

Motivation

Previously, model-related configuration was scattered in the labels HashMap as untyped strings. This made it:

• Hard to discover what fields existed
• Easy to have typos in field names
• Impossible to have per-model configuration on multi-model workers

Now model config is properly typed in ModelCard with IDE autocomplete and compile-time checking.

Changes

1. Worker trait methods - Changed signature from fn tokenizer_path(&self) to fn tokenizer_path(&self, model_id: &str) (same for reasoning_parser, tool_parser, chat_template)

2. WorkerBuilder - Added models(Vec<ModelCard>) and model(ModelCard) builder methods

3. CreateWorkerStep - Creates ModelCard from WorkerConfigRequest instead of storing in labels

Test plan

• All 531 existing tests pass
• New tests for model-aware method behavior
• Verified worker_to_info() returns correct model config