Add iOS app with CarPlay and Siri

SwiftUI port of the Android app under ios/, with CarPlay browse and
Now Playing, Siri play-media intents, and a build-ipa.sh script that
makes an unsigned IPA for sideloading. README gets an iOS section and
the vibecoded disclaimer.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

README.md

@@ -1,3 +1,5 @@
+### ⚠️ THIS PROJECT WAS ENTIRELY VIBECODED AND IS SLOP. DO NOT PROCEED IF YOU DO NOT ALIGN WITH THESE VALUES. DO NOT COMPLAIN ABOUT IT IN PULL RELEASES, ISSUES, ETC. UNLESS THERE ARE SEVERE SECURITY RISKS. THEY WILL BE REMOVED. PROCEED AT YOUR OWN RISK! ⚠️
+
 # Stemify
 
 **Your whole music library, taken apart and put back together however you like.**
@@ -25,6 +27,7 @@ pressing the "mute vocals" button at exactly the wrong moment.
 - [Stem Now: skipping the line](#stem-now-skipping-the-line)
 - [The Equalizer](#the-equalizer)
 - [Android Auto](#android-auto)
+- [iOS and CarPlay](#ios-and-carplay)
 - [The desktop apps](#the-desktop-apps)
 - [Separation models](#separation-models)
 - [How the pieces find each other](#how-the-pieces-find-each-other)
@@ -356,6 +359,21 @@ adb forward tcp:5277 tcp:5277
 
 ---
 
+## iOS and CarPlay
+
+`ios/` is a SwiftUI port of the Android app with the same features, plus CarPlay (browse tabs, Now Playing with Vocals and Mix buttons) and Siri ("play X in Stemify"). iOS 17 or newer.
+
+Build an unsigned IPA on a Mac with Xcode and xcodegen (`brew install xcodegen`):
+
+```
+cd ios
+scripts/build-ipa.sh      # writes build/Stemify.ipa
+```
+
+Sideload `build/Stemify.ipa` with Sideloadly or AltStore, which sign it with your Apple ID. To work in Xcode instead, run `xcodegen generate` and open `Stemify.xcodeproj`.
+
+CarPlay and Siri need the `carplay-audio` and `siri` entitlements. A free Apple ID can't sign those, so on a free sideload the app works on the phone but won't show up in CarPlay or Siri. A paid developer account covers Siri; CarPlay audio also needs Apple to approve the entitlement for your team.
+
 ## The desktop apps
 
 ### Stemify (the separator)