Reframe collatz-conjecture exercise instructions as a story (#2508)

* split into introduction and instructions

* update metadata

* make instructions more clear

* incorporate forum suggestions

* fix lint errors

* Apply suggestions from code review

Co-authored-by: Isaac Good <IsaacG@users.noreply.github.com>

---------

Co-authored-by: Isaac Good <IsaacG@users.noreply.github.com>

exercises/collatz-conjecture/instructions.md

@@ -0,0 +1,3 @@
+# Instructions
+
+Given a positive integer, return the number of steps it takes to reach 1 according to the rules of the Collatz Conjecture.

exercises/collatz-conjecture/introduction.md

@@ -0,0 +1,28 @@
+# Introduction
+
+One evening, you stumbled upon an old notebook filled with cryptic scribbles, as though someone had been obsessively chasing an idea.
+On one page, a single question stood out: **Can every number find its way to 1?**
+It was tied to something called the **Collatz Conjecture**, a puzzle that has baffled thinkers for decades.
+
+The rules were deceptively simple.
+Pick any positive integer.
+
+- If it's even, divide it by 2.
+- If it's odd, multiply it by 3 and add 1.
+
+Then, repeat these steps with the result, continuing indefinitely.
+
+Curious, you picked number 12 to test and began the journey:
+
+12 ➜ 6 ➜ 3 ➜ 10 ➜ 5 ➜ 16 ➜ 8 ➜ 4 ➜ 2 ➜ 1
+
+Counting from the second number (6), it took 9 steps to reach 1, and each time the rules repeated, the number kept changing.
+At first, the sequence seemed unpredictable — jumping up, down, and all over.
+Yet, the conjecture claims that no matter the starting number, we'll always end at 1.
+
+It was fascinating, but also puzzling.
+Why does this always seem to work?
+Could there be a number where the process breaks down, looping forever or escaping into infinity?
+The notebook suggested solving this could reveal something profound — and with it, fame, [fortune][collatz-prize], and a place in history awaits whoever could unlock its secrets.
+
+[collatz-prize]: https://mathprize.net/posts/collatz-conjecture/

exercises/collatz-conjecture/metadata.toml

@@ -1,4 +1,4 @@
 title = "Collatz Conjecture"
 blurb = "Calculate the number of steps to reach 1 using the Collatz conjecture."
-source = "An unsolved problem in mathematics named after mathematician Lothar Collatz"
-source_url = "https://en.wikipedia.org/wiki/3x_%2B_1_problem"
+source = "Wikipedia"
+source_url = "https://en.wikipedia.org/wiki/Collatz_conjecture"