fix(cortex-cli): accept uppercase shell names in completion command

Fixes bounty issue #1551

The completion command now accepts shell names in any case (e.g., BASH, Bash, bash)
by adding ignore_case = true to the shell argument attribute in CompletionCommand.

Author: factorydroid

cortex-cli/src/main.rs

@@ -275,7 +275,7 @@ struct LogoutCommand {
 #[derive(Args)]
 struct CompletionCommand {
     /// Shell to generate completions for
-    #[arg(value_enum, default_value_t = Shell::Bash)]
+    #[arg(value_enum, default_value_t = Shell::Bash, ignore_case = true)]
     shell: Shell,
 }