refactor(runs): remove legacy tokens from run output header (#4721)

## Description

Remove the trace header's parsed values in favor of a nudge to using AI
metadata. Any step whose output looks like an LLM response will now show
a nudge.

### Before
<img width="1266" height="959" alt="Screenshot 2026-08-06 at 9 55 18 AM"
src="https://github.com/user-attachments/assets/4e4b1336-28c4-43ec-8366-6a7bde36da5d"
/>

### After
<img width="1266" height="959" alt="Screenshot 2026-08-06 at 9 53 09 AM"
src="https://github.com/user-attachments/assets/9920321c-14b7-41e1-866c-0d998d393fa3"
/>


## Release note

Removed Model/token values parsed from `step.run` output in favor of a
nudge towards the better AI metadata setup.



## Migration note

<!-- Upgrade, deployment, config, schema, or compatibility notes. Use
"None" if none. -->
None.

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