Support @latest

[mxcl]

Closes #1160

[Copilot]

Pull Request Overview

This PR implements support for the "@latest" specifier in package requests by refactoring package resolution logic and updating related functionality.

• Made the inventory module public and added semver type aliases in the library.
• Updated the inventory functions to accept project names instead of full package requests and adjusted error messages accordingly.
• Refactored CLI resolution logic to support "@latest", bumped Cargo.toml versions, and added a CI test for the new behavior.

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
crates/lib/src/lib.rs	Made the inventory module public and introduced type aliases for semver.
crates/lib/src/inventory.rs	Modified the ls function to receive a project name and updated error messaging.
crates/lib/Cargo.toml	Bumped the library version from 0.5.0 to 0.6.0.
crates/cli/src/x.rs	Updated the environment variable assignment for PKGX_VERSION.
crates/cli/src/resolve.rs	Refactored package resolution logic using a new Pkgspec enum to support "@latest".
crates/cli/Cargo.toml	Updated the CLI version from 2.5.0 to 2.6.0 and bumped the libpkgx dependency.
.github/workflows/ci.yml	Added a CI test to validate the "@latest" support.

[jhheider]

Mmm, discriminated unions.

[coveralls]

coverage: 89.099%. first build
when pulling 6a6d511 on latest
into 8d288f0 on main.