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/stop-on-colour-change.mdx

@@ -3,61 +3,17 @@ title: "Activity: Stop On Colour Change"
 date: "2021-06-03"
 categories: ["Activities", "All"]
 tags: ["Colour Sensors", "Branching", "Iteration"]
+codingSkills: ["Branching", "Iteration"]
+roverConcepts: ["Colour"]
 excerpt: "Learn branching, iteration, and how to use the colour sensors."
 featuredImage: "/images/resources/stop-on-colour-change.png"
 ---
 
 Program the rover to keep moving forward until it detects a change of floor colour with the colour sensors. Once it detects this colour, stop the rover.
 
-####
-  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/HJSQU3Jaar8" title="Stop on Colour Change Activity Demonstration" frameBorder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowFullScreen></iframe>
 
 ### Setup