fix: preserve Markdown blocks when copying messages (#2944)

* fix: preserve Markdown blocks when copying messages

* fix: preserve blank lines when copying code

---------

Co-authored-by: Iuliia Ivashko <yulia.ivashko@gmail.com>

packages/ui/src/lib/messages/messageText.ts

@@ -1,6 +1,7 @@
 import type { Part } from '@opencode-ai/sdk/v2';
 
 type TextLikePart = Part & { text?: string; content?: string };
+type UserTextPart = Part & { text?: string; content?: string; shellAction?: { output?: unknown; command?: unknown } };
 
 export const flattenAssistantTextParts = (parts: Part[]): string => {
     const textParts = parts
@@ -8,8 +9,36 @@ export const flattenAssistantTextParts = (parts: Part[]): string => {
         .map((part) => (part.text || part.content || '').trim())
         .filter((text) => text.length > 0);
 
-    const combined = textParts.join('\n');
-    return combined.replace(/\n\s*\n+/g, '\n');
+    return textParts.join('\n\n');
+};
+
+export const flattenUserTextParts = (parts: Part[]): string => {
+    const textParts = parts.filter((part): part is UserTextPart => part?.type === 'text');
+
+    const shellOutputs = textParts
+        .map((part) => {
+            const output = part.shellAction?.output;
+            return typeof output === 'string' ? output.trim() : '';
+        })
+        .filter((output) => output.length > 0);
+    if (shellOutputs.length > 0) {
+        return shellOutputs.join('\n\n');
+    }
+
+    const shellCommands = textParts
+        .map((part) => {
+            const command = part.shellAction?.command;
+            return typeof command === 'string' ? command.trim() : '';
+        })
+        .filter((command) => command.length > 0);
+    if (shellCommands.length > 0) {
+        return shellCommands.join('\n');
+    }
+
+    const plainTexts = textParts
+        .map((part) => (part.text || part.content || '').trim())
+        .filter((text) => text.length > 0);
+    return plainTexts.join('\n\n');
 };
 
 export const suggestPlanTitleFromText = (text: string): string => {