Fix command help text: Replace Codex with LLMX in CLI descriptions

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Co-Authored-By: Claude <noreply@anthropic.com>

llmx-rs/chatgpt/src/apply_command.rs

@@ -11,7 +11,7 @@ use crate::get_task::OutputItem;
 use crate::get_task::PrOutputItem;
 use crate::get_task::get_task;
 
-/// Applies the latest diff from a Codex agent task.
+/// Applies the latest diff from a LLMX agent task.
 #[derive(Debug, Parser)]
 pub struct ApplyCommand {
     pub task_id: String,