Skip non-matching platform binaries during resolve

[Codex]

Which issue does this PR resolve?

Linux installs for codex failed because the resolver fell back to the package name when platform-specific binaries didn’t match, leading to searches for a non-existent codex binary inside the Linux archive.

Description of this PR

• Platform filtering: PkgDef::resolve now drops binaries whose platform-specific names don’t match the current platform instead of falling back to the package name, preventing phantom lookups on Linux codex archives.
• Tests: Updated platform-specific resolution tests to assert skipping unmatched binaries and Linux-only retention of the codex payload.

Example:

let pkg_def = make_pkg_def(vec![BinDef {
    name: Some(PlatformAwareString::ByPlatform(
        [("nonexistent-platform-xyz".into(), "bin".into())].into(),
    )),
    link: None,
}]);

// Previously produced a fallback entry; now yields no binaries on non-matching platforms.
assert!(pkg_def.resolve("codex").bin.is_empty());

[Copilot]

Pull request overview

This PR updates platform-aware binary resolution so that binaries whose platform-specific names don’t match the current platform are skipped during PkgDef::resolve, preventing incorrect fallback lookups (notably for Linux codex installs).

Changes:

• Adjust PkgDef::resolve to skip non-matching platform-mapped binary names rather than falling back to the package name.
• Rename/update a unit test to assert that non-matching platform entries are skipped.
• Update the codex TOML deserialization + resolution test expectations (Linux keeps only the Linux payload).

Comments suppressed due to low confidence (1)

src/package.rs:129

• b.name is moved by value in the match, which partially moves b and makes the later access to b.link illegal (this should fail to compile). Borrow b.name (e.g., match &b.name) or destructure BinDef { name, link } up-front so both fields can be used while still allowing resolve_for_platform() returning None to skip the binary.

                    // Resolve name from PlatformAwareString; if it doesn't match the current
                    // platform, skip this binary instead of falling back to the package name.
                    let raw_name = match b.name {
                        Some(s) => s.resolve_for_platform(),
                        None => Some(pkg_name.to_string()),
                    }?;
                    let name = normalize_name(raw_name);

                    // Resolve link from PlatformAwareString, defaulting to the resolved name
                    let raw_link =
                        b.link.as_ref().and_then(|s| s.resolve_for_platform()).unwrap_or_else(|| name.clone());
                    let link = normalize_name(raw_link);

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[Copilot]

The Windows-only assertions contain a duplicate assert_eq!(resolved.bin.len(), 3); (it appears twice), which is redundant and adds noise to the test. Remove one of them (and keep the one that best matches the comment) to make failures clearer.

Suggested change

assert_eq!(resolved.bin.len(), 3);