Feature Request: Support per-task model override for Kanban workers

Problem

Currently, Kanban workers always use the model configured in their assigned profile's config.yaml. There is no way to specify a different model at the task level.

When a task is dispatched, the worker spawns via:

hermes -p <profile> --skills kanban-worker chat -q work kanban task <id>

No --model argument is passed, so the worker always falls back to the profile's configured model.

Expected Behavior

The kanban create command should accept a --model option (e.g., --model deepseek-v3) that gets forwarded to the worker's startup command:

hermes -p <profile> --model <model> --skills kanban-worker chat -q work kanban task <id>

This would allow users to route specific tasks to specific models without creating a dedicated profile for each model.

Related Issues

• Profile config fallback_providers not inherited by kanban worker agents #23362: Profile config fallback_providers not inherited by kanban worker agents
• delegate_task model parameter silently discarded — subagents always inherit parent model #23467: delegate_task model parameter silently discarded — subagents always inherit parent model

Both issues confirm that task-level model routing is a known gap in the architecture.

Suggested Implementation

1. hermes_cli/kanban_db.py — _default_spawn()
   Add --model <task.model> to the worker subprocess command when task.model is set.

2. hermes_cli/kanban.py — create command
   Add --model option that stores the model name in Task.model field.

3. Database migration
   Add a model column to the tasks table (nullable — defaults to null meaning "use profile default").

Priority

Medium — workaround exists (create a profile per model), but adds unnecessary overhead for users who want model-aware task routing.