Updates: Model Management (#8248)

## Summary

Model management improvements: refactored tag API, enhanced UX for
trigger phrases and editing.

## Changes

### API Refactor
- Add `addAssetTags` (POST) and `removeAssetTags` (DELETE) endpoints in
assetService
- `updateAssetTags` now computes diff and calls remove/add serially
- Add `TagsOperationResult` schema; cache syncs with server response

### UX Improvements
- **Trigger phrases**: click to copy individual phrases, copy-all button
in header
- **Display name**: show edit icon on hover instead of relying on
double-click
- **Model type**: show plain text when immutable instead of disabled
select
- **Tags input**: only show edit icon on hover
- **Field labels**: updated styling to use muted foreground color
- **Optimistic update** for model type selection

---------

Co-authored-by: Amp <amp@ampcode.com>
Co-authored-by: coderabbitai[bot] <136622811+coderabbitai[bot]@users.noreply.github.com>
Co-authored-by: GitHub Action <action@github.com>

src/components/ui/button/button.variants.ts

@@ -26,7 +26,8 @@ export const buttonVariants = cva({
       md: 'h-8 rounded-lg p-2 text-xs',
       lg: 'h-10 rounded-lg px-4 py-2 text-sm',
       icon: 'size-8',
-      'icon-sm': 'size-5 p-0'
+      'icon-sm': 'size-5 p-0',
+      unset: ''
     }
   },