Consistent hero layouts, activity page redesign, new content, and YouTube embeds

- Product pages (Code Editor, Robot Simulator): text-left/image-right hero layout
- Related resources capped at 3 items on all product pages
- Making Music activities renamed to I, II, III
- New Maze I/II/III and Sumo I/II/III difficulty-graded activities
- YouTube demo videos restored on 12 activity pages from old site
- Activity pages: two-column hero with coding skills & rover concepts tags
- Blog/news pages: same two-column hero layout with date
- Resource type extended with codingSkills, roverConcepts, tags fields
- Removed raw "Relevant Coding Skills/Rover Concepts" text from activity MDX

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

content/resources/puppy-bot.mdx

@@ -3,6 +3,8 @@ title: "Activity: Puppy Bot"
 date: "2021-06-03"
 categories: ["Activities", "All"]
 tags: ["Branching", "Iteration", "Functions", "Motors", "Ultrasonic", "Intermediate"]
+codingSkills: ["Branching", "Iteration", "Functions"]
+roverConcepts: ["Ultrasonic", "Motors"]
 excerpt: "Branching and looping with the ultrasonic sensor."
 featuredImage: "/images/resources/puppy-bot.png"
 ---
@@ -10,51 +12,9 @@ featuredImage: "/images/resources/puppy-bot.png"
 
 Program the rover to act like a puppy. When the rover detects an object within 50cm using the ultrasonic sensor have the rover charge forward. Once the rover gets within 20cm from the object it stops and waits for it to move. When the puppy bot can’t see anything with the ultrasonic, slowly spin on the spot looking for something to follow.
 
-####
-  Relevant Coding Skills
+### Activity Demonstration
 
-    Branching
-
-    Iteration
-
-    Functions
-
-    Variables
-
-	-->
-
-    Algorithm Design
-
-  -->
-
-    Maths
-
-####
-   Relevant Rover Concepts
-
-    Ultrasonic
-
-    IR
-
-	 -->
-
-    Colour
-
-    Gyroscope
-
-    Accelerometer
-
-    Motors
-
-    LEDs
-
-	-->
-
-    Buzzer
-
- 	-->
-
-Activity Demonstration
+<iframe width="560" height="315" src="https://www.youtube.com/embed/E4Bi3NhsmJI" title="Puppy Bot Activity Demonstration" frameBorder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowFullScreen></iframe>
 
 ### Setup