[Refactor] Keep model selection out of workspace routing

[roomote-roomote]

​Opened on behalf of @mrubens. Follow up by mentioning @roomote-roomote, in the web UI, or in Slack.

What changed

• Removed task-model selection from the workspace router prompt, response schema, context, result types, and diagnostics.
• Stopped auto-routed Slack and web launches from applying a model inferred from task text while preserving explicit model choices supplied by the caller.
• Removed the router-specific model eval dataset and focused tests that covered the retired behavior.

Why this change was made

Running agents can now switch models directly. Keeping model interpretation in the workspace router duplicated that responsibility and forced tasks to start on an inferred model before the agent could handle the request itself.

Impact

Auto-routing now decides only where a task should run. Model directives remain in the task prompt for the running agent, while explicit launch-time model selections continue to work through their existing paths.

[roomote-community]

No code issues found. See task

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