fix: generate SDK and Stylus sidebars before validating links in CI

The validate-sidebar-links workflow was failing because both sdk-sidebar.js
and stylus-by-example sidebar files are generated (gitignored) and didn't
exist in CI. The workflow now:

1. Initializes submodules (arbitrum-sdk, stylus-by-example)
2. Installs SDK dependencies
3. Syncs Stylus content to generate stylus-by-example sidebars
4. Generates SDK docs via TypeDoc to create sdk-sidebar.js
5. Validates sidebar links

This matches the Vercel production build flow and ensures all required
sidebar files exist before validation.

Changes:
- Enable recursive submodule checkout
- Add step to install SDK dependencies
- Add step to sync Stylus content
- Add step to generate SDK docs via TypeDoc

Author: anegg0

.github/workflows/validate-sidebar-links.yml

@@ -41,11 +41,24 @@ jobs:
         with:
           install-command: yarn install --frozen-lockfile
 
+<<<<<<< HEAD
       - name: Install SDK dependencies
         run: yarn install-sdk-dependencies
 
       - name: Generate SDK docs
         run: yarn generate-sdk-docs
 
+||||||| parent of 4003ad2a6 (fix: generate SDK and Stylus sidebars before validating links in CI)
+=======
+      - name: Install SDK dependencies
+        run: yarn install-sdk-dependencies
+
+      - name: Sync Stylus content
+        run: yarn sync-stylus-content
+
+      - name: Generate SDK docs
+        run: yarn generate-sdk-docs
+
+>>>>>>> 4003ad2a6 (fix: generate SDK and Stylus sidebars before validating links in CI)
       - name: Validate sidebar links
         run: yarn tsx scripts/check-sidebar-links.ts