Change horizontal scrollbar to show when needed not just bottom page (#1257)

closes
RaspberryPiFoundation/digital-editor-issues#877

**### Screenshots:**

**Scrollbar at the bottom with no vertical scroll:**
<img width="654" height="572" alt="image"
src="https://github.com/user-attachments/assets/69d48146-67db-4390-820d-045a8d0edd06"
/>

**Scrollbar still there when vertical scroll:**
<img width="654" height="572" alt="image"
src="https://github.com/user-attachments/assets/4ffcdf0c-f3cb-4829-9741-47dd8b5a8d2f"
/>

Author: jamiebenstead

CHANGELOG.md

@@ -4,6 +4,12 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/), and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+
+### Changed
+
+- Changed the horizontal scrollbar to show without needing to scroll to the bottom of the editor window (#1257)
+
 ## [0.33.0] - 2025-10-15
 
 ### Added

src/assets/stylesheets/EditorPanel.scss

@@ -6,13 +6,15 @@
   // Needed here for vertical scroll
   overflow: auto;
   scrollbar-width: thin;
+  height: 100%;
 }
 
 .editor {
   display: flex;
   flex-flow: column;
   flex: 1;
   overflow: hidden;
+  height: 100%;
 
   .cm-editor {
     flex: 1;