context_servers: Add ability to provide labels for prompt outputs (#17077)

Server can now include an optional description in a `prompts/get`
response. Zed will displayed the description as label of the slash
command.

Release Notes:

- context_servers: Servers can provide an optional description in
`prompts/get` responses that is displayed as the slash command label.

crates/assistant/src/slash_command/context_server_command.rs

@@ -84,11 +84,15 @@ impl SlashCommand for ContextServerSlashCommand {
 
                 Ok(SlashCommandOutput {
                     sections: vec![SlashCommandOutputSection {
-                        range: 0..result.len(),
+                        range: 0..(result.prompt.len()),
                         icon: IconName::ZedAssistant,
-                        label: SharedString::from(format!("Result from {}", prompt_name)),
+                        label: SharedString::from(
+                            result
+                                .description
+                                .unwrap_or(format!("Result from {}", prompt_name)),
+                        ),
                     }],
-                    text: result,
+                    text: result.prompt,
                     run_commands_in_text: false,
                 })
             })