fix(editor): handle / paths in interceptor (#4793)

Fixes FER-7568

## Short description of the changes made
- ensure we handle `/` routes properly in interceptor

## What was the motivation & context behind this PR?
- fix issue where tabs with plain `/` route were going to a not found page

## How has this PR been tested?
- tested with postman

Author: sbawabe

packages/fern-dashboard/src/components/editor/link-interceptor.test.ts

@@ -199,7 +199,7 @@ describe("getInterceptedLink", () => {
 
             const result = getInterceptedLink(event, defaultMetadata);
 
-            expect(result).toBe("/test-org/editor/test-docs/main/");
+            expect(result).toBe("/test-org/editor/test-docs/main/root");
         });
 
         it("should handle empty path", () => {

packages/fern-dashboard/src/components/editor/link-interceptor.ts

@@ -1,3 +1,5 @@
+import { ROOT_SLUG_ALIAS } from "@fern-docs/components/navigation";
+
 export const getInterceptedLink = (
     event: MouseEvent,
     metadata: {
@@ -35,6 +37,11 @@ export const getInterceptedLink = (
         return `/${orgName}/editor/${docsUrl}/${branch}/${cleanHref}`;
     }
 
+    // Handle root path - forward to ROOT_SLUG_ALIAS
+    if (cleanBasePath == "" && cleanHref === "") {
+        return `/${orgName}/editor/${docsUrl}/${branch}/${ROOT_SLUG_ALIAS}`;
+    }
+
     // Otherwise, add the base path prefix
     const basePathPrefix = cleanBasePath ? `${cleanBasePath}/` : "";
     return `/${orgName}/editor/${docsUrl}/${branch}/${basePathPrefix}${cleanHref}`;