Update code block styles

Author: dhruvisompura

src/vs/workbench/contrib/positronNotebook/browser/markdownRenderer.ts

@@ -108,7 +108,10 @@ function markedHighlight(options: marked.MarkedOptions & {
 			code({ text, lang, escaped }: marked.Tokens.Code) {
 				const classAttr = lang ? ` class="language-${escape(lang)}"` : '';
 				text = text.replace(/\n$/, '');
-				return `<pre><code${classAttr}>${escaped ? text : escape(text)}\n</code></pre>`;
+				// Note: We intentionally omit the trailing \n that marked-highlight includes.
+				// The \n is preserved by <pre>'s default white-space:pre behavior
+				// this causes visible whitespace at the bottom of code blocks in Positron notebooks.
+				return `<pre><code${classAttr}>${escaped ? text : escape(text)}</code></pre>`;
 			},
 		},
 	};

src/vs/workbench/contrib/positronNotebook/browser/notebookCells/Markdown.css

@@ -142,10 +142,18 @@
 		border-radius: 4px;
 	}
 
+	/** code block styling */
+	pre {
+		background-color: var(--vscode-textCodeBlock-background);
+		padding: 16px;
+		border-radius: 4px;
+	}
+
 	pre code {
 		line-height: 1.357em;
 		white-space: pre-wrap;
 		padding: 0;
+		background-color: transparent; /* override inline code style */
 	}
 
 	li p {