fix(SkillFileSystemHelper): fix单个技能存在则不保存其他技能

[superjvjkdf]

AgentScope-Java Version

1.0.10
[The version of AgentScope-Java you are working on, e.g. 1.0.9, check your pom.xml dependency version or run mvn dependency:tree | grep agentscope-parent:pom(only mac/linux)]

Description

[Please describe the background, purpose, changes made, and how to test this PR]
当技能目录已存在且强制覆盖标志为false时，现在将跳过该技能而不是返回失败状态。这样可以保存后续技能而不会因为单个技能的存在而导致其他技能无法保存。

Checklist

Please check the following items before code is ready to be reviewed.

• Code has been formatted with mvn spotless:apply
• All tests are passing (mvn test)
• Javadoc comments are complete and follow project conventions
• Related documentation has been updated (e.g. links, examples, etc.)
• Code is ready for review

[cla-assistant]

All committers have signed the CLA.

[cla-assistant]

Thank you for your submission! We really appreciate it. Like many open source projects, we ask that you sign our Contributor License Agreement before we can accept your contribution.
_{You have signed the CLA already but the status is still pending? Let us recheck it.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!