fix: honor android sdk mirror url

[jdx]

Summary

• read ANDROID_SDK_MIRROR_URL from the process environment in both version discovery and pre-install hooks
• resolve metadata and relative download URLs against the configured mirror
• add a mocked-hook regression test covering both hooks
• run unit tests with Lua in CI so hook behavior and syntax are actually exercised

Root cause

The hooks attempted to read the variable from the vfox env module, where it was always nil. The vfox runtime exposes process environment variables through os.getenv.

Validation

• mise x stylua@latest -- stylua --check metadata.lua hooks test/mirror_url.lua
• mise x actionlint@latest -- actionlint .github/workflows/test.yml
• mise x lua@5.4 -- ./test/run.sh

Resolves #6.

[gemini-code-assist]

Code Review

This pull request replaces the custom env module with os.getenv to retrieve the ANDROID_SDK_MIRROR_URL environment variable in both available.lua and pre_install.lua hooks. It also introduces a new test script (test/mirror_url.lua) and integrates it into the test suite (test/run.sh) to verify mirror URL handling. Feedback suggests normalizing the base_url by stripping any trailing slashes to prevent double slashes when constructing URLs.

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[gemini-code-assist]

If the user configures ANDROID_SDK_MIRROR_URL with a trailing slash (e.g., https://mirror.example/android/), appending /repository2-3.xml will result in a URL with double slashes (https://mirror.example/android//repository2-3.xml). Some strict HTTP servers or proxies might reject this or return a 404.

It is safer to normalize the base_url by stripping any trailing slashes.

    local base_url = (os.getenv("ANDROID_SDK_MIRROR_URL") or "https://dl.google.com/android/repository"):gsub("/+$", "")

[gemini-code-assist]

If the user configures ANDROID_SDK_MIRROR_URL with a trailing slash, appending /repository2-3.xml or / followed by the relative URL will result in double slashes. Normalizing the base_url by stripping trailing slashes ensures robust URL construction.

    local base_url = (os.getenv("ANDROID_SDK_MIRROR_URL") or "https://dl.google.com/android/repository"):gsub("/+$", "")