feat(vscode-ide-companion/markdown): add copy button to code blocks in markdown renderer

packages/vscode-ide-companion/src/webview/components/MarkdownRenderer/MarkdownRenderer.css

@@ -159,6 +159,47 @@
   line-height: 1.5;
 }
 
+.markdown-content .code-block-wrapper {
+  position: relative;
+}
+
+.markdown-content .code-block-wrapper pre {
+  /* Reserve space so the copy button never overlaps code text */
+  padding-top: 2rem; /* room for the button height */
+  padding-right: 2.4rem; /* room for the button width */
+}
+
+.markdown-content .code-block-wrapper .copy-button {
+  position: absolute;
+  top: 6px;
+  right: 6px;
+  padding: 2px 8px;
+  font-size: 12px;
+  line-height: 1.6;
+  border-radius: 4px;
+  border: 1px solid var(--app-primary-border-color);
+  background-color: var(--app-elevated-background, rgba(255, 255, 255, 0.06));
+  color: var(--app-secondary-foreground);
+  cursor: pointer;
+  z-index: 1;
+  opacity: 0; /* show on hover to reduce visual noise */
+  transition: opacity 100ms ease-in-out;
+}
+
+.markdown-content .code-block-wrapper:hover .copy-button,
+.markdown-content .code-block-wrapper .copy-button:focus {
+  opacity: 1;
+}
+
+.markdown-content .code-block-wrapper .copy-button:hover {
+  background-color: var(--app-list-hover-background, rgba(127, 127, 127, 0.1));
+}
+
+.markdown-content .code-block-wrapper .copy-button:disabled {
+  opacity: 0.7;
+  cursor: default;
+}
+
 .markdown-content pre code {
   background: none;
   border: none;

packages/vscode-ide-companion/src/webview/components/MarkdownRenderer/MarkdownRenderer.tsx

@@ -45,29 +45,43 @@ export const MarkdownRenderer: React.FC<MarkdownRendererProps> = ({
       typographer: true,
     } as MarkdownItOptions);
 
-    // Add syntax highlighting for code blocks
+    // Add syntax highlighting + a copy button for code blocks
     md.use((md) => {
+      const renderWithCopy = (token: {
+        info: string;
+        content: string;
+      }): string => {
+        const lang = (token.info || 'plaintext').trim();
+        const content = token.content;
+
+        // Wrap in a container so we can position a copy button
+        return (
+          `<div class="code-block-wrapper">` +
+          `<button class="copy-button" data-lang="${md.utils.escapeHtml(lang)}" aria-label="Copy code block">Copy</button>` +
+          `<pre class="code-block language-${md.utils.escapeHtml(lang)}"><code class="language-${md.utils.escapeHtml(lang)}">${md.utils.escapeHtml(content)}</code></pre>` +
+          `</div>`
+        );
+      };
+
       md.renderer.rules.code_block = function (
         tokens,
         idx: number,
         _options,
         _env,
       ) {
-        const token = tokens[idx];
-        const lang = token.info || 'plaintext';
-        const content = token.content;
-
-        // Add syntax highlighting classes
-        return `<pre class="code-block language-${lang}"><code class="language-${lang}">${md.utils.escapeHtml(content)}</code></pre>`;
+        const token = tokens[idx] as unknown as {
+          info: string;
+          content: string;
+        };
+        return renderWithCopy(token);
       };
 
       md.renderer.rules.fence = function (tokens, idx: number, _options, _env) {
-        const token = tokens[idx];
-        const lang = token.info || 'plaintext';
-        const content = token.content;
-
-        // Add syntax highlighting classes
-        return `<pre class="code-block language-${lang}"><code class="language-${lang}">${md.utils.escapeHtml(content)}</code></pre>`;
+        const token = tokens[idx] as unknown as {
+          info: string;
+          content: string;
+        };
+        return renderWithCopy(token);
       };
     });
 
@@ -228,13 +242,41 @@ export const MarkdownRenderer: React.FC<MarkdownRendererProps> = ({
     return container.innerHTML;
   };
 
-  // Event delegation: intercept clicks on generated file-path links
+  // Event delegation: intercept clicks on copy buttons and generated file-path links
   const handleContainerClick = (
     e: React.MouseEvent<HTMLDivElement, MouseEvent>,
   ) => {
     const target = e.target as HTMLElement | null;
     if (!target) return;
 
+    // Handle copy button clicks for fenced code blocks
+    const copyBtn = (target.closest &&
+      target.closest('button.copy-button')) as HTMLButtonElement | null;
+    if (copyBtn) {
+      e.preventDefault();
+      e.stopPropagation();
+
+      try {
+        const wrapper = copyBtn.closest('.code-block-wrapper');
+        const codeEl = wrapper?.querySelector('pre code');
+        const text = codeEl?.textContent ?? '';
+        if (text) {
+          void navigator.clipboard.writeText(text);
+          // Quick feedback
+          const original = copyBtn.textContent || 'Copy';
+          copyBtn.textContent = 'Copied';
+          copyBtn.disabled = true;
+          setTimeout(() => {
+            copyBtn.textContent = original;
+            copyBtn.disabled = false;
+          }, 1200);
+        }
+      } catch (err) {
+        console.warn('Copy failed:', err);
+      }
+      return;
+    }
+
     // Find nearest anchor with our marker class
     const anchor = (target.closest &&
       target.closest('a.file-path-link')) as HTMLAnchorElement | null;