Fix duplicated output in Code Mode by filtering content by audience

The shell tool returns two Content::text items: one for the assistant and
one for the user. For short outputs both contain identical text. The
callback in code_execution_extension was joining all text content without
filtering by audience, causing the output to appear twice.

Filter to only include content targeted at the assistant (or with no
audience restriction) before joining text results.

crates/goose/src/agents/code_execution_extension.rs

@@ -7,7 +7,7 @@ use pctx_code_mode::model::{CallbackConfig, ExecuteInput, GetFunctionDetailsInpu
 use pctx_code_mode::{CallbackRegistry, CodeMode};
 use rmcp::model::{
     CallToolRequestParams, CallToolResult, Content, Implementation, InitializeResult, JsonObject,
-    ListToolsResult, ProtocolVersion, RawContent, ServerCapabilities, Tool as McpTool,
+    ListToolsResult, ProtocolVersion, RawContent, Role, ServerCapabilities, Tool as McpTool,
     ToolAnnotations, ToolsCapability,
 };
 use schemars::{schema_for, JsonSchema};
@@ -272,9 +272,16 @@ fn create_tool_callback(
                         if let Some(sc) = &result.structured_content {
                             Ok(serde_json::to_value(sc).unwrap_or(Value::Null))
                         } else {
+                            // Filter to assistant-audience or no-audience content,
+                            // skipping user-only content to avoid duplicated output
                             let text: String = result
                                 .content
                                 .iter()
+                                .filter(|c| {
+                                    c.audience().is_none_or(|audiences| {
+                                        audiences.is_empty() || audiences.contains(&Role::Assistant)
+                                    })
+                                })
                                 .filter_map(|c| match &c.raw {
                                     RawContent::Text(t) => Some(t.text.clone()),
                                     _ => None,