style: improve spacing on Hypothesis slides

- Shorten headings from h3 to h4 to prevent wrapping
- Add vertical space after intro text on slide 22
- Add vertical space before command on slide 38

Co-Authored-By: Claude Opus 4.5 <[email protected]>

Author: Gordon J. Köhn

docs/slides.qmd

@@ -557,9 +557,11 @@ class SimulationResult(BaseModel):
 
 **Flip the playbook:** Don't write examples. Describe *properties* that must always hold.
 
+ 
+
 ::: {.columns}
 ::: {.column width="50%"}
-### ❌ Example-based: You pick the cases
+#### ❌ Example-based
 
 ```python
 def test_sort():
@@ -573,7 +575,7 @@ You test what you think of. Bugs hide in what you don't.
 :::
 
 ::: {.column width="50%"}
-### ✓ Property-based: Computer picks the cases
+#### ✓ Property-based
 
 ```python
 from hypothesis import given, strategies as st
@@ -980,6 +982,8 @@ def test_remove_duplicates(items):
         assert all(items.index(y) > original_idx for y in result[i+1:] if y != x)
 ```
 
+ 
+
 ```bash
 pixi run pytest demos/demo_hypothesis.py -v --hypothesis-show-statistics
 ```