Generate shared schemes for the iOS and watch apps

XcodeGen wrote no scheme files by default, so Xcode fell back to stale
xcuserdata that omitted the iOS app — leaving the Workouts scheme absent
from the run destination dropdown. Declare scheme blocks on both app
targets so real shared schemes are generated.

Claude-Session: https://claude.ai/code/session_01SCv7zvGFcKy47KSTnTLxRe

project.yml

@@ -67,6 +67,8 @@ targets:
         ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME: AccentColor
         TARGETED_DEVICE_FAMILY: "1"
         DEVELOPMENT_ASSET_PATHS: "\"Workouts/Preview Content\""
+    scheme:
+      testTargets: []
 
   # ---- watchOS app (no iCloud; syncs through the phone via WatchConnectivity) -
   Workouts Watch App:
@@ -101,6 +103,8 @@ targets:
         ASSETCATALOG_COMPILER_GLOBAL_ACCENT_COLOR_NAME: AccentColor
         TARGETED_DEVICE_FAMILY: "4"
         DEVELOPMENT_ASSET_PATHS: "\"Workouts Watch App/Preview Content\""
+    scheme:
+      testTargets: []
 
   # ---- watchOS widget extension (a launcher complication for the watch face) --
   Workouts Watch Widget: