Preserve cask container metadata

[MikeMcQuaid]

Fixes #23094

• Retain nested paths and explicit types for API-backed downloads.
• Ensure queued staging extracts the declared nested container.

---

• Have you followed our Contributing guidelines?
• Have you checked for other open Pull Requests for the same change?
• Have you explained what your changes do? Performance claims (e.g. "this is faster") must include Hyperfine benchmarks.
• Have you explained why you'd like these changes included, not just what they do?
• For bug fixes, have you given step-by-step brew commands to reproduce the bug?
• Have you written new tests (excluding integration tests)? Here's an example.
• Have you successfully run brew lgtm (style, typechecking and tests) locally?

---

• AI was used to generate or assist with generating this PR.

OpenAI Codex 5.5 xhigh with local review and testing.

---

[Copilot]

Pull request overview

This PR fixes a regression/bug in queued cask staging for API-backed installs by ensuring container metadata (including nested: and explicit type:) is preserved when constructing the Cask::Download object from API structs, so nested-container extraction occurs during DownloadQueue staging.

Changes:

• Populate container stanza (nested path + type) when building API-backed Cask objects for downloads.
• Add a regression spec verifying queued staging extracts a declared nested container for an API-loaded cask.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
Library/Homebrew/api/cask_download.rb	Ensures API-backed downloads retain container metadata so queued staging can extract nested containers correctly.
Library/Homebrew/test/cask/installer_spec.rb	Adds a regression test covering nested-container extraction when using DownloadQueue staging for an API-loaded cask.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.