fix: always generate preview workflow during onboarding regardless of devBranch

The preview yml was silently skipped when the repo had no branch named
"develop" (scan returns developmentBranch: null) and the user didn't
explicitly set a development branch during onboarding — causing the
initial preview deployment to never trigger.

The workflow template already defaults to "develop" when devBranch is
null, so the && input.devBranch guard was stricter than needed. Removing
it ensures shipbrain-preview.yml is always written during initial setup.

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

Author: JeevantheDev

lib/github/setup.ts

@@ -243,9 +243,10 @@ export function workflowFiles(input: WorkflowInput) {
     files[".github/workflows/shipbrain-ci.yml"] = shipbrainCiWorkflowMinimal(input);
   }
 
-  // Include preview workflow if Cloudflare is enabled and develop branch exists
-  // Skip if preview workflow already exists (unless force overwrite)
-  if (input.includeCloudflare && input.devBranch && (force || !input.previewExists)) {
+  // Always include preview workflow when Cloudflare is enabled.
+  // devBranch is optional — the template defaults to "develop" when null.
+  // Skip only if the workflow already exists (unless force overwrite).
+  if (input.includeCloudflare && (force || !input.previewExists)) {
     files[".github/workflows/shipbrain-preview.yml"] = shipbrainPreviewWorkflow(input);
   }