Fix critical nested result structure in tools/call - remove incorrect result.result nesting

- tools/call was incorrectly nesting ScreenAsMcpTool result: result.result = [content: ...]
- ScreenAsMcpTool already returns correct structure: result = [content: ...]
- Creates nested result.result.result which breaks MCP spec and client parsing
- Fix: Extract content directly from serviceResult.result instead of nesting
- Resolves opencode client error: 'Typeundefined is not an object (evaluating result.content)'
- Now result.content correctly accesses content array as expected by MCP clients

@@ -265,9 +265,10 @@
                         }
                     }
                     
-                    result.result = [
+                    // Extract content from ScreenAsMcpTool result, don't nest it
+                    result = serviceResult?.result ?: [
                         content: content,
-                        isError: serviceResult?.result?.isError ?: false
+                        isError: false
                     ]
                     return
                 }