enhance(frontend/aiscript): セーブ内容を削除できるMk:removeを追加

[kakkokari-gtyih]

What

かいてあるとおり

Why

Fix #15141

Additional info (optional)

Checklist

• Read the contribution guide
• Test working in a local environment
• (If needed) Add story of storybook
• (If needed) Update CHANGELOG.md
• (If possible) Add tests

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 7 lines in your changes missing coverage. Please review.

Project coverage is 19.31%. Comparing base (f123be3) to head (26954e1).

Files with missing lines	Patch %	Lines
packages/frontend/src/scripts/aiscript/api.ts	0.00%	7 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           develop   #15158       +/-   ##
============================================
- Coverage    39.95%   19.31%   -20.64%     
============================================
  Files         1563      728      -835     
  Lines       197878   103878    -94000     
  Branches      3635      991     -2644     
============================================
- Hits         79059    20066    -58993     
+ Misses      118215    83258    -34957     
+ Partials       604      554       -50     

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