feat: add proxy support for ripgrep download

[dipfocus]

Description

• Added support for using a proxy (https_proxy/HTTPS_PROXY) when downloading ripgrep.
• The download process will automatically use the proxy if one is configured, and will work as usual if no proxy is set.

Checklist

• [x] I've read the contributing guide
• [x] The relevant docs, if any, have been updated or created
• [x] The relevant tests, if any, have been updated or created

Screenshots

N/A

Tests

• Manually tested ripgrep download with and without a proxy environment. Both scenarios work as expected.

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✨ No issues found! Your code is sparkling clean! ✨

[Patrick-Erichsen]

Thanks for the contribution here @dipfocus ! Once you sign the CLA we can get this merged 👍

Also appears to be a prettier issue: https://github.com/continuedev/continue/actions/runs/15624381783/job/44015762325?pr=6106#step:5:6

[dipfocus]

I have read the CLA Document and I hereby sign the CLA