feat(tracing): failure traces on by default in CI

docs-site/docs/guides/trace-viewer.md

@@ -14,7 +14,7 @@ Selenium Boot generates a standalone, self-contained HTML trace viewer per test
 
 ## Enabling Trace Recording
 
-Trace recording is opt-in and configured in `selenium-boot.yml`:
+Trace recording is configured in `selenium-boot.yml`. When `tracing.enabled` is not set, traces for **failed tests are recorded automatically in CI** (detected from `CI`, `GITHUB_ACTIONS`, `JENKINS_URL` and similar) and stay off on your machine. An explicit `enabled: true` or `enabled: false` always wins.
 
 ```yaml title="selenium-boot.yml"
 tracing:

src/main/java/com/seleniumboot/ci/GitHubActionsSummary.java

@@ -110,7 +110,7 @@ public static boolean appendSummary(SeleniumBootConfig config,
             return false;
         }
         SeleniumBootConfig.Tracing tracing = config.getTracing();
-        if (tracing == null || !tracing.isEnabled()) {
+        if (tracing == null || !tracing.isEffectivelyEnabled()) {
             return false;
         }
         if (timings == null || timings.isEmpty() || summaryFile == null) {

src/main/java/com/seleniumboot/config/SeleniumBootConfig.java

@@ -520,12 +520,18 @@ public static final class Flakiness {
     }
 
     public static final class Tracing {
-        private boolean enabled       = false;
+        /** null = not set in selenium-boot.yml; resolved by {@link #isEffectivelyEnabled(boolean)}. */
+        private Boolean enabled       = null;
         private boolean captureOnPass = false;
 
-        public boolean isEnabled()              { return enabled; }
+        /** The value set in selenium-boot.yml; false when unset. Prefer {@link #isEffectivelyEnabled()}. */
+        public boolean isEnabled()              { return Boolean.TRUE.equals(enabled); }
         public void    setEnabled(boolean v)    { this.enabled = v; }
 
+        /** An explicit {@code tracing.enabled} wins; when unset, tracing is on in CI and off locally. */
+        public boolean isEffectivelyEnabled()   { return isEffectivelyEnabled(com.seleniumboot.ci.CiEnvironmentDetector.isCI()); }
+        public boolean isEffectivelyEnabled(boolean ci) { return enabled != null ? enabled : ci; }
+
         public boolean isCaptureOnPass()           { return captureOnPass; }
         public void    setCaptureOnPass(boolean v) { this.captureOnPass = v; }
     }

src/main/java/com/seleniumboot/junit5/SeleniumBootExtension.java

@@ -306,7 +306,7 @@ static String testId(ExtensionContext context) {
     private void saveTraceIfEnabled(String testId, String testName, boolean isPassing) {
         try {
             SeleniumBootConfig.Tracing tracing = SeleniumBootContext.getConfig().getTracing();
-            if (tracing == null || !tracing.isEnabled()) return;
+            if (tracing == null || !tracing.isEffectivelyEnabled()) return;
             if (isPassing && !tracing.isCaptureOnPass()) return;
             TraceRecorder.save(testId, testName);
         } catch (Exception ignored) {}

src/main/java/com/seleniumboot/listeners/TestExecutionListener.java

@@ -402,7 +402,7 @@ private void runAiAnalysisIfEnabled(String testId, String pageUrl, String pageTi
     private void saveTraceIfEnabled(String testId, String testName, boolean isPassing) {
         try {
             SeleniumBootConfig.Tracing tracing = SeleniumBootContext.getConfig().getTracing();
-            if (tracing == null || !tracing.isEnabled()) return;
+            if (tracing == null || !tracing.isEffectivelyEnabled()) return;
             if (isPassing && !tracing.isCaptureOnPass()) return;
             TraceRecorder.save(testId, testName);
         } catch (Exception ignored) {}

src/test/java/com/seleniumboot/unit/TracingConfigTest.java

@@ -0,0 +1,36 @@
+package com.seleniumboot.unit;
+
+import com.seleniumboot.config.SeleniumBootConfig;
+import org.testng.annotations.Test;
+
+import static org.testng.Assert.assertFalse;
+import static org.testng.Assert.assertTrue;
+
+public class TracingConfigTest {
+
+    @Test
+    public void unsetFollowsCiEnvironment() {
+        SeleniumBootConfig.Tracing tracing = new SeleniumBootConfig.Tracing();
+        assertTrue(tracing.isEffectivelyEnabled(true), "unset tracing is on in CI");
+        assertFalse(tracing.isEffectivelyEnabled(false), "unset tracing stays off locally");
+    }
+
+    @Test
+    public void explicitFalseWinsInCi() {
+        SeleniumBootConfig.Tracing tracing = new SeleniumBootConfig.Tracing();
+        tracing.setEnabled(false);
+        assertFalse(tracing.isEffectivelyEnabled(true));
+    }
+
+    @Test
+    public void explicitTrueWinsLocally() {
+        SeleniumBootConfig.Tracing tracing = new SeleniumBootConfig.Tracing();
+        tracing.setEnabled(true);
+        assertTrue(tracing.isEffectivelyEnabled(false));
+    }
+
+    @Test
+    public void captureOnPassStaysOffByDefault() {
+        assertFalse(new SeleniumBootConfig.Tracing().isCaptureOnPass());
+    }
+}