refactor: extend Tag component state API to support surface/neutral chip color

## Summary

In PR #10673 (migrate PrimeVue Chip → custom Tag), `SearchFilterChip.vue` had to fall back to a hardcoded `bg-surface-700` Tailwind class because the Tag component's `state` prop currently only exposes `default`, `unselected`, and `selected` — none of which map to the surface/neutral color needed for search filter chips.

## Proposed follow-up

Extend the Tag component's state API (e.g., add a `surface` or `neutral` state) so that `SearchFilterChip.vue` can use the convention-aligned state prop instead of the raw palette override:

```diff
-
+
```

This will keep chip coloring within the shared Tag design system and avoid hardcoded surface classes across components.

## References

- PR: https://github.com/Comfy-Org/ComfyUI_frontend/pull/10673
- Review comment: https://github.com/Comfy-Org/ComfyUI_frontend/pull/10673#discussion_r3179658427
- Requested by: @christian-byrne

┆Issue is synchronized with this [Notion page](https://www.notion.so/Issue-11923-refactor-extend-Tag-component-state-API-to-support-surface-neutral-chip-color-3566d73d36508159afd9f67f8ce3cf3d) by [Unito](https://www.unito.io)