[Bug]: Floorp Fluerial 使用時にUIが想定通りに動作していない

[kota6-me]

Pre-Submission Checklist

• [X] I have checked the existing/closed issues to ensure this issue has not already been reported.
• [X] I am using the latest supported version of the browser.
• [X] I have tried disabling all browser extensions/add-ons to rule out interference from these.
• [X] I have tried clearing the browser cache and cookies.
• [X] I have checked with a new profile and the issue still occurs.
• [X] I have provided detailed step-by-step instructions on how to reproduce the issue.
• [X] I have included relevant screenshots or console outputs.
• [ ] I have checked that this problem is not occurring in the latest version of Firefox ESR.
• [X] This issue is specific to this browser and does not occur in other browsers.

Bug Summary

FloorpFluerialデザイン使用時に、タブバーの「現在開いているタブ」が他のものと識別できなくなってしまっている。

Reproduction Steps

1. 設定>>デザイン よりFloorpFluerialデザインを有効にする

Expected Behavior

使用中のタブのみ、他のタブと違う色になる。

Actual Behavior

使用中のタブも他のタブと同一の色になっている。

Screenshots

Browser Version

バージョン 11.21.0 (64 ビット) | Firefox: 128.5.0

Operating System

Windows 10 Home - 22H2(19045.5198)

Additional Context

https://discord.com/channels/877135925707173889/1313093632324276254