📝 Document requirement of legacy preview execution

DEVELOPER.md

@@ -59,19 +59,23 @@ In order to properly test everything, you will want to use the _PHP Monitor EAP_
 
 If you would like to run the unit tests outside of Xcode, you can run:
 
+```sh
 xcodebuild test \
     -project "PHP Monitor.xcodeproj" \
     -scheme "Unit Tests" \
     -destination "platform=macOS" \
     -parallel-testing-enabled NO
+```
 
 ### UI tests
 
+```sh
 xcodebuild test \
     -project "PHP Monitor.xcodeproj" \
     -scheme "PHP Monitor" \
     -destination "platform=macOS" \
     -only-testing "UI Tests"
+```
     
 ### Failures in UI tests
 
@@ -97,6 +101,22 @@ You can enable marketing mode by setting the `PHPMON_MARKETING_MODE` environment
 
     launchctl setenv PHPMON_MARKETING_MODE true
     
+## 👀 Previews (`#Preview`)
+
+Xcode may have issues rendering various previews, like:
+
+```swift
+#Preview {
+    HeaderView(text: "Hello world").frame(width: 330.0)
+}
+```
+
+I've noticed this is an issue on recent versions of Xcode (26.x) on macOS Tahoe (26.x). This likely has something to do with the new preview execution system that doesn't play nice with the particular way PHP Monitor has been set up (which is somewhat of a legacy project).
+
+So, in order to ensure these previews render correctly, go to **Editor > Canvas > Use Legacy Previews Execution**. 
+
+This may help resolve any timeouts, but you must first build the project or you will get an error about caches.
+
 ## 🐛 Symbolication of crashes
 
 The easiest way to symbolicate crashes is to simply rename the file to `.crash`, and drag it into Xcode.