Fix HTML semantics in script run instructions

This commit corrects HTML semantic errors in browser instruction dialogs
displayed when a script is downloaded via browser.

Key changes:

- Fix HTML structure by removing `<ul>` and `<ol>` tags from `<p>`
  elements
- Replace `<code>` with `<kbd>` for keyboard inputs

Other supporting changes:

- Improve clarity readability of some instructions
- Add CSS styles for `<kbd>`

src/presentation/assets/styles/base/_index.scss

@@ -53,3 +53,17 @@ sup {
   vertical-align: super;
   font-size: $font-size-relative-smallest;
 }
+
+kbd {
+  font-family: unset; // Reset the default browser styles
+  background-color: $color-primary-dark;
+  border: 1px solid $color-primary-darker;
+  border-radius: 0.2em;
+  box-shadow: inset 0 1px 0 0 $color-primary-dark, inset 0 -2px 0 0 $color-primary-darker;
+  font-family: $font-family-monospace;
+  font-size: $font-size-relative-smallest;
+  padding: $spacing-relative-x-small $spacing-relative-x-small;
+  text-align: center;
+  user-select: none;
+  white-space: nowrap;
+}