feat(dx): add Swift development environment

[joshyorko]

🦅 The Swift Predator Strikes

"London is nice, but Paris is nicer... and Swift is swiftest."

---

Summary

This PR adds Swift development support to Bluefin DX by adding a Brewfile that will be discoverable via ujust bbrew.

Changes

File	Description
system_files/bluefin/usr/share/ublue-os/homebrew/swift.Brewfile	Brewfile with opinionated Swift packages

Packages Included

Package	Purpose
swiftly	Official Swift toolchain manager from swift.org
swiftlint	Enforce Swift style and conventions
swiftformat	Automatic code formatting

Usage

ujust bbrew              # Select "swift" from the list
swiftly install latest   # Install the Swift compiler

Test Plan

• Build Bluefin DX image with updated common layer
• Verify "swift" appears as an option in ujust bbrew
• Select swift and confirm brew bundle installs successfully
• Verify swiftly install latest works after installation

---

Closes ublue-os/bluefin#2655

[dosubot]

Documentation Updates

2 document(s) were updated by changes in this PR:

bluefin

• Bluefin Newsletter (View Changes)
• ujust Commands (View Changes)

^{How did I do? Any feedback?}  

[castrojo]

We're moving away from top level ujust commands, having the brewfile in the right place so swift shows up in ujust bbrew would match the new pattern. Thanks!

[joshyorko]

Thanks @castrojo! Updated the PR:

• ✅ Removed swift.just (no top-level ujust swift command)
• ✅ Reverted 00-entry.just to original
• ✅ Kept only swift.Brewfile so it shows up in ujust bbrew

Users will now: ujust bbrew → select "swift" → done.

Is this the pattern you are speaking to?