fix(rbac): guard noUncheckedIndexedAccess in name derivation and newStaff insert

With noUncheckedIndexedAccess:true, split("@")[0] returns string|undefined,
making `name` typed as string|undefined and failing the notNull staff.name
insert constraint. Fix by using ?? fallback on the array access.

Also add newStaff null guard after .returning() destructure — array
destructuring yields T|undefined with noUncheckedIndexedAccess enabled.

src/middleware/rbac.ts

@@ -127,15 +127,14 @@ export const resolveStaffMiddleware: MiddlewareHandler<AppEnv> = async (
 
     if (oidcAccount) {
       // Derive name: prefer jwt.name, fall back to email prefix, then "Unknown"
-      const name =
-        jwt.name?.trim() ||
-        (jwt.email ? jwt.email.split("@")[0] : "Unknown");
+      const emailPrefix = jwt.email.split("@")[0] ?? "Unknown";
+      const name = jwt.name?.trim() || emailPrefix;
 
       const [newStaff] = await db
         .insert(staff)
         .values({
           userId: jwt.sub,
-          email: jwt.email ?? "",
+          email: jwt.email,
           name,
           role: "groomer",
           isSuperUser: false,
@@ -143,6 +142,10 @@ export const resolveStaffMiddleware: MiddlewareHandler<AppEnv> = async (
         })
         .returning();
 
+      if (!newStaff) {
+        return c.json({ error: "Forbidden: auto-provision failed" }, 500);
+      }
+
       console.log(
         `[rbac] auto-provisioned staff record for OIDC user: ${jwt.sub} -> staff:${newStaff.id} (${name})`
       );