generics: add explanatory commentary to solution

src/generics/solution.md

@@ -3,3 +3,22 @@
 ```rust,editable
 {{#include exercise.rs:solution}}
 ```
+
+The solution uses trait bounds to constrain the generic type `T`:
+
+- **Trait Bounds:** The `<T: Ord>` syntax requires that any type used with `min`
+  must implement the `Ord` trait, which guarantees a total ordering.
+- **Comparison:** The `cmp` method returns an `Ordering` enum (`Less`, `Equal`,
+  or `Greater`), which we handle with pattern matching.
+
+<details>
+
+- **`Ord` vs. `PartialOrd`:** Rust distinguishes between types that have a total
+  order (`Ord`) and those that only have a partial order (`PartialOrd`).
+  Floating-point numbers (`f32`, `f64`) only implement `PartialOrd` because
+  `NaN` cannot be compared. Consequently, this `min` function cannot be called
+  with floats.
+- **Standard Library:** In real-world code, one would typically use the built-in
+  `std::cmp::min` function or the `.min()` method available on many types.
+
+</details>