fix: DrillOrbit fades in/out at path edges, DrillBitSpinner uses radial mask instead of hard clip

Former-commit-id: 3aea27f3e17984634206ca817d074b18e712933e

components/blocks/HeroSection.tsx

@@ -5,6 +5,7 @@ import { Badge, Container, Heading } from '@/components/ui';
 import { Button } from '@/components/ui/Button';
 import { DrillOrbit } from '@/components/ui/decorations/DrillOrbit';
 import { DrillBitSpinner } from '@/components/ui/decorations/DrillBitSpinner';
+import { DrillTeeth } from '@/components/ui/decorations/DrillTeeth';
 
 export interface HeroSectionProps {
   title: string;
@@ -78,6 +79,8 @@ export const HeroSection: React.FC<HeroSectionProps> = (props) => {
         </div>
         {/* Decorative: abstract HDD bore trajectory */}
         <DrillOrbit side="right" />
+        {/* Organic wave divider — displaced earth strata */}
+        <DrillTeeth position="bottom" fill="var(--color-primary-dark)" />
       </section>
     </Reveal>
   );