feat: add local workflow web console

src/cli.ts

@@ -24,6 +24,7 @@ import {
 } from "./workflow-engine.js";
 import { WorkflowConfigError } from "./workflow-config.js";
 import { WorkflowLockError } from "./workflow-state.js";
+import { startWorkflowWebServer } from "./workflow-web.js";
 
 async function main() {
   let args: WorkflowArgs;
@@ -91,12 +92,22 @@ async function main() {
         });
         break;
 
+      case "web":
+        await startWorkflowWebServer(args.port);
+        // Keep the process alive
+        await new Promise(() => {});
+        break;
+
       default: {
         const _exhaustive: never = args;
         throw new Error(`Unknown subcommand: ${(_exhaustive as any).sub}`);
       }
     }
-  } catch (err) {
+  } catch (err: any) {
+    if (err && err.code === "EADDRINUSE") {
+      process.stderr.write(`Error: Port is already in use.\n`);
+      process.exit(1);
+    }
     if (err instanceof WorkflowEngineError) {
       process.stderr.write(`Error: ${err.message}\n`);
       process.exit(err.exitCode);