enhance guessing mimetype of tool file

[QunBB]

Summary

fix #17731

Tip

Close issue syntax: Fixes #<issue number> or Resolves #<issue number>, see documentation for more details.

Screenshots

Before	After
...	...

Before:

After:

Checklist

Important

Please review the checklist below before submitting your pull request.

• This change requires a documentation update, included: Dify Document
• I understand that this PR may be closed in case there was no previous discussion or issues. (This doesn't apply to typos!)
• I've added a test for each change that was introduced, and I tried as much as possible to make a single atomic change.
• I've updated the documentation accordingly.
• I ran dev/reformat(backend) and cd web && npx lint-staged(frontend) to appease the lint gods

[crazywoola]

Please link an existing issue in the description.

[QunBB]

Oh, i don't find the related issue, so should i open an issue for the description?

[QunBB]

@crazywoola I have created a corresponding issue myself. You could check it again to decide whether to merge this pull request or i close it.