fix: use iOS 18 runtime for simulator tests (iOS 19 breaks WebKit Inspector)

iOS 19's WebKit Inspector Protocol has breaking changes — many domains
(Runtime, DOM, CSS, CPUProfiler, Worker, etc.) return "domain was not
found" when accessed through ios-webkit-debug-proxy. Use iOS 18 runtime
on CI for full domain support.

- CI: select Xcode 16 (iOS 18) if available on the runner
- sim-setup.sh: prefer iOS 18 or lower runtimes over iOS 19+

Author: nnemirovsky

.github/workflows/test.yml

@@ -86,6 +86,25 @@ jobs:
       - name: Install ios-webkit-debug-proxy
         run: brew install ios-webkit-debug-proxy
 
+      - name: Select Xcode with iOS 18 runtime
+        run: |
+          # iOS 19+ has breaking WebKit Inspector Protocol changes (many
+          # domains return "not found"). Use an older Xcode/iOS for testing.
+          echo "Available Xcode versions:"
+          ls -d /Applications/Xcode*.app 2>/dev/null || true
+          echo ""
+          # Prefer Xcode 16 (iOS 18) over Xcode 17 (iOS 19)
+          for xcode in /Applications/Xcode_16*.app; do
+            if [ -d "$xcode" ]; then
+              echo "Selecting $xcode"
+              sudo xcode-select -s "$xcode"
+              break
+            fi
+          done
+          echo "Active Xcode: $(xcode-select -p)"
+          echo "Available runtimes:"
+          xcrun simctl list runtimes
+
       - name: Boot iOS Simulator and start iwdp
         run: |
           eval "$(./scripts/sim-setup.sh)"

scripts/sim-setup.sh

@@ -36,18 +36,27 @@ pkill -f ios_webkit_debug_proxy 2>/dev/null || true
 sleep 1
 
 # 1. Find an available iPhone simulator.
+# Prefer iOS 18 or lower — iOS 19+ has breaking WebKit Inspector Protocol changes
+# where many domains (Runtime, DOM, etc.) return "domain was not found" through iwdp.
 DEVICE_NAME=$(xcrun simctl list devices available --json | \
   python3 -c "
-import json, sys
+import json, sys, re
 data = json.load(sys.stdin)
-for runtime, devs in sorted(data['devices'].items(), reverse=True):
+candidates = []
+for runtime, devs in data['devices'].items():
     if 'iOS' not in runtime and 'SimRuntime.iOS' not in runtime:
         continue
+    m = re.search(r'iOS[- ](\d+)', runtime)
+    ver = int(m.group(1)) if m else 0
     for d in devs:
         if 'iPhone' in d['name'] and d['isAvailable']:
-            print(d['name'])
-            sys.exit(0)
-print('', end='')
+            candidates.append((ver, runtime, d['name']))
+if not candidates:
+    print('', end='')
+    sys.exit(0)
+# Sort: prefer iOS 18 and below (ver <= 18 first, descending), then 19+ as fallback
+candidates.sort(key=lambda x: (0 if x[0] <= 18 else 1, -x[0]))
+print(candidates[0][2])
 ")
 
 if [ -z "$DEVICE_NAME" ]; then