Add simple Rust install deps

[MikeMcQuaid]

• teach install to plan and pour simple runtime dependency trees before linking the requested formula.
• cover the new path in tests/cli.rs and note the aview smoke test in README.md because libaacs still falls back to Ruby.
• record that brew fetch aalib aview was needed here while the Rust GHCR downloader still fails on uncached bottles.

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Used OpenAI Codex plus local testing/review.

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[Copilot]

Pull request overview

This PR expands the experimental brew-rs install command to handle “simple” runtime dependency trees (bottle-only, no complex dependency metadata) by planning and pouring dependencies before linking the requested formula, with accompanying test coverage and updated smoke-test documentation.

Changes:

• Add an install planner to resolve and execute a simple dependency install plan (pour/link actions) instead of requiring a leaf-only bottle.
• Add a CLI test covering install of a bottle formula with a simple runtime dependency.
• Document the current real-world smoke test (aview + aalib) and current Rust GHCR download limitations.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

File	Description
Library/Homebrew/rust/brew-rs/src/commands/install.rs	Adds dependency-aware install planning and execution for simple runtime dependency trees.
Library/Homebrew/rust/brew-rs/tests/cli.rs	Adds coverage for installing and linking a formula plus a simple runtime dependency.
Library/Homebrew/rust/brew-rs/README.md	Documents current install smoke test and notes current downloader behavior.

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