fix(dts-plugin): Add https-proxy-agent support for HTTP-only corporate proxies

[Copilot]

The dts-plugin was unable to fetch remote MFE TypeScript typings (@mf-types.zip and @mf-types.d.ts files) in corporate environments with HTTP-only proxies. The issue occurred because Node's default https.Agent doesn't handle HTTPS requests through HTTP-only proxies - it doesn't send the required CONNECT request for tunneling.

This change adds support for HTTP-only proxies by:

1. Adding https-proxy-agent dependency (v7.0.5) to handle HTTPS requests through HTTP proxies
2. Enhancing axiosGet function to detect proxy environment variables and conditionally use HttpsProxyAgent
3. Maintaining backward compatibility with existing configurations

The implementation detects proxy configuration from environment variables (HTTP_PROXY, HTTPS_PROXY, http_proxy, https_proxy) with preference for HTTPS_PROXY over HTTP_PROXY, and automatically switches between:

• HttpsProxyAgent when proxy is configured (with proxy: false to disable axios built-in proxy)
• Standard https.Agent when no proxy is configured

Example of the corporate environment this fixes:

export HTTP_PROXY=http://proxy.company.com:8080
export HTTPS_PROXY=http://proxy.company.com:8080  # Note: http:// protocol for HTTPS proxy

The solution follows the exact approach suggested in the issue using https-proxy-agent and includes comprehensive test coverage for all proxy scenarios while preserving existing functionality like the family parameter for IPv4/IPv6 selection.

Fixes #3981.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• download.cypress.io

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

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