feat: add /api/list-workflows route to enumerate workflow directories

Scans subdirectories of a given parent path for valid workflow JSON files,
returning name, path, node count, and last modified time.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/app/api/list-workflows/route.ts

@@ -0,0 +1,82 @@
+import { NextRequest, NextResponse } from "next/server";
+import * as fs from "fs/promises";
+import * as path from "path";
+import { validateWorkflowPath } from "@/utils/pathValidation";
+
+interface WorkflowListEntry {
+  name: string;
+  directoryPath: string;
+  nodeCount: number;
+  lastModified: number;
+}
+
+export async function GET(request: NextRequest) {
+  const parentPath = request.nextUrl.searchParams.get("path");
+
+  if (!parentPath) {
+    return NextResponse.json(
+      { success: false, error: "Path parameter required" },
+      { status: 400 }
+    );
+  }
+
+  const pathValidation = validateWorkflowPath(parentPath);
+  if (!pathValidation.valid) {
+    return NextResponse.json(
+      { success: false, error: pathValidation.error },
+      { status: 400 }
+    );
+  }
+
+  try {
+    const entries = await fs.readdir(parentPath, { withFileTypes: true });
+    const directories = entries.filter((e) => e.isDirectory());
+
+    const workflows: WorkflowListEntry[] = [];
+
+    for (const dir of directories) {
+      const dirPath = path.join(parentPath, dir.name);
+      try {
+        const files = await fs.readdir(dirPath);
+        const jsonFiles = files.filter((f) => f.endsWith(".json"));
+
+        for (const jsonFile of jsonFiles) {
+          try {
+            const filePath = path.join(dirPath, jsonFile);
+            const content = await fs.readFile(filePath, "utf-8");
+            const parsed = JSON.parse(content);
+
+            if (parsed.version && parsed.nodes && parsed.edges) {
+              const stat = await fs.stat(filePath);
+              workflows.push({
+                name: parsed.name || dir.name,
+                directoryPath: dirPath,
+                nodeCount: parsed.nodes.length,
+                lastModified: stat.mtimeMs,
+              });
+              break; // Use first valid workflow file per directory
+            }
+          } catch {
+            continue;
+          }
+        }
+      } catch {
+        // Skip directories we can't read
+        continue;
+      }
+    }
+
+    // Sort by most recently modified first
+    workflows.sort((a, b) => b.lastModified - a.lastModified);
+
+    return NextResponse.json({ success: true, workflows });
+  } catch (error) {
+    return NextResponse.json(
+      {
+        success: false,
+        error: error instanceof Error ? error.message : "Failed to list workflows",
+      },
+      { status: 500 }
+    );
+  }
+}