- Removes `model` field from task item/schema, TaskParams, and TaskItem types.
- Removes model selector validation, formatting, and approval display logic.
- Updates task tool priority docs to reflect that model is no longer per-call overridable.
- Updates eval agent() helper docs and prompt templates to remove model parameter.
- Updates tests to reflect removal of model override capability.
- Renamed task wire fields, replacing `assignment` and `description` with `task` and `name` while removing `role` references.
- Implemented automated task UI label generation using a tiny model to replace manual role descriptions.
- Updated task execution and rendering logic to support per-item agent resolution and dynamic badge display.
- Migrated schemas, prompts, and test suites to enforce the new flat task structure and agent-centric policy.
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