feat(scenario): dump page screenshot and HTML to run files on step failure

Captures a full-page screenshot and the current page HTML whenever a
scenario or snippet step fails, and uploads both as run artifacts so
failures can be diagnosed from the run's file list.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

server/src/scenario/scenario-scheduler.service.ts

@@ -515,6 +515,8 @@ export class ScenarioSchedulerService implements OnModuleInit {
       `Step ${(stepRun.scenarioStep as ScenarioStepEntity | undefined)?.order ?? "?"} failed: ${description}`,
     );
 
+    await this.dumpPageOnFailure(stepRun);
+
     // Cancel all remaining waiting/pending step runs in this run
     await this.runStepRepo
       .createQueryBuilder()
@@ -534,4 +536,51 @@ export class ScenarioSchedulerService implements OnModuleInit {
     await this.runRepo.update(stepRun.runId, { status: "fail" });
     this.logger.log(`Run #${stepRun.runId} → fail`);
   }
+
+  // ── Page dump on failure ────────────────────────────────────────────────────
+
+  private async dumpPageOnFailure(
+    stepRun: ScenarioRunStepEntity,
+  ): Promise<void> {
+    const handle = this.runBrowsers.get(stepRun.runId);
+    if (!handle) return; // no browser was ever opened for this run (e.g. setup error)
+
+    const step = stepRun.scenarioStep as ScenarioStepEntity | undefined;
+    const namePrefix = `step-${step?.order ?? stepRun.id}-failure`;
+
+    try {
+      const screenshot = await handle.page.screenshot({ fullPage: true });
+      await this.fileStorageService.createAndSaveRunArtifact(
+        stepRun.runId,
+        screenshot,
+        `${namePrefix}.png`,
+        "image/png",
+      );
+    } catch (err) {
+      this.logger.warn(
+        `StepRun #${stepRun.id}: failed to capture failure screenshot — ${(err as Error).message}`,
+      );
+    }
+
+    try {
+      const html = await handle.page.content();
+      await this.fileStorageService.createAndSaveRunArtifact(
+        stepRun.runId,
+        Buffer.from(html, "utf-8"),
+        `${namePrefix}.html`,
+        "text/html",
+      );
+    } catch (err) {
+      this.logger.warn(
+        `StepRun #${stepRun.id}: failed to capture failure page HTML — ${(err as Error).message}`,
+      );
+    }
+
+    this.persistLog(
+      stepRun.runId,
+      stepRun.id,
+      "log",
+      `Step ${step?.order ?? "?"} failed: page dump uploaded to run files`,
+    );
+  }
 }