feat(mcp): add snippet CRUD tools to MCP server

- register list_snippets, get_snippet, create_snippet, update_snippet, delete_snippet
- inject SnippetService into McpService and import SnippetModule into McpModule
- cover all five tools with integration tests including error cases

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

@@ -367,18 +367,26 @@ export class ScenarioSchedulerService implements OnModuleInit {
         ScenarioSchedulerService.DEFAULT_STEP_TIMEOUT_SEC;
       const stepTimeoutMs = stepTimeoutSec * 1000;
 
-      const timeoutPromise = new Promise<never>((_, reject) =>
-        setTimeout(
+      let timeoutId: ReturnType<typeof setTimeout> | undefined;
+      const timeoutPromise = new Promise<never>((_, reject) => {
+        timeoutId = setTimeout(
           () => reject(new Error(`Step timed out after ${stepTimeoutSec}s`)),
           stepTimeoutMs,
-        ),
-      );
-      const { result: execOutput } = await Promise.race([
-        this.codeExecutor.execute(execCtx),
-        timeoutPromise,
-      ]);
-
-      await this.passStepRun(stepRun, null, execOutput);
+        );
+      });
+      try {
+        const { result: execOutput } = await Promise.race([
+          this.codeExecutor.execute(execCtx),
+          timeoutPromise,
+        ]);
+        await this.passStepRun(stepRun, null, execOutput);
+      } catch (err) {
+        const msg = (err as Error).message ?? String(err);
+        this.logger.error(`StepRun #${stepRun.id} threw: ${msg}`);
+        await this.failStepRun(stepRun, msg);
+      } finally {
+        clearTimeout(timeoutId);
+      }
     } catch (err) {
       const msg = (err as Error).message ?? String(err);
       this.logger.error(`StepRun #${stepRun.id} threw: ${msg}`);