Stagger build numbers by platform: iOS/watch even, macOS odd

Both platforms share one App Store Connect build-number space (same
bundle ID, universal purchase), so the raw commit count would collide.
The vendored script partitions on PLATFORM_NAME; watchOS rides with iOS
because the embedded watch app's CFBundleVersion must match its host.

project.yml

@@ -28,12 +28,19 @@ packages:
     url: https://git.rzen.dev/rzen/indie-backup.git
     from: "2.0.0"
 
-# Shared post-build phase — stamps CFBundleVersion (git commit count), BuildDate, and
-# BuildHash into each target's (and dSYM's) Info.plist. Aliased into every code-bearing
-# target below so the app, watch app, and both widget extensions stamp identical metadata.
+# Shared post-build phase — stamps CFBundleVersion, BuildDate, and BuildHash into each
+# target's (and dSYM's) Info.plist. Vendored at Scripts/update_build_info.sh (not the
+# shared indie-skills copy) because the iOS app and Workouts Mac share ONE App Store
+# Connect record (dev.rzen.indie.Workouts, universal purchase), so both stamping the
+# raw commit count would collide on upload. The script partitions the space instead:
+# iOS + watchOS targets get an EVEN CFBundleVersion (commit-count*2), the Mac target
+# gets ODD (commit-count*2+1) — derived from PLATFORM_NAME inside the script, so this
+# one anchor still serves all five code-bearing targets unmodified. watchOS is grouped
+# with iOS (not given its own parity) because the embedded watch app's CFBundleVersion
+# must match its host iOS app's exactly.
 scriptAnchors:
   updateBuildInfo: &updateBuildInfo
-    - script: '"${SRCROOT}/../indie-skills/skills/app-versioning/scripts/update_build_info.sh"'
+    - script: '"${SRCROOT}/Scripts/update_build_info.sh"'
       name: Update Build Info
       shell: /bin/sh
       basedOnDependencyAnalysis: false