Add HTML anchor linking between lessons and reference documents for improved navigation

skills/productivity/teach/SKILL.md

@@ -40,6 +40,8 @@ The lesson should teach ONE THING only. It should be completable very quickly -
 
 Make opening a lesson as easy as possible — ideally a single CLI command the user can run to open the HTML file in their browser.
 
+Each lesson should link via HTML anchors to other lessons and reference documents.
+
 ## The Mission
 
 Every lesson should be tied into the mission - the reason that the user is interested in learning about the topic.
@@ -48,6 +50,8 @@ If the user is unclear about the mission, or the `MISSION.md` is not populated,
 
 Failing to understand the mission will mean knowledge acquisition is not grounded in real-world goals. Lessons will feel too abstract. You will have no way of judging what the user should do next.
 
+Missions may change as the user develops more skills and knowledge. This is normal - make sure to update the `MISSION.md` and add a learning record to capture the change. Confirm with the user before changing the mission.
+
 ## Zone Of Proximal Development
 
 Each lesson, the learner should always feel as if they are being challenged 'just enough'.