fix: update slash command count and add /setup assertion in test

- Update slash_command_specs().len() assertion from 139 to 140.
  The /setup command added by this PR increased the spec count by 1
  but the test's expected count was not updated, causing CI failure.

- Add assert!(help.contains("/setup")) to the
  renders_help_from_shared_specs test so the new command is
  verified in the help output.

  Fixes CI Build ❌ and Test ❌ on #3218.

rust/crates/commands/src/lib.rs

@@ -6011,7 +6011,8 @@ mod tests {
         assert!(help.contains("aliases: /skill"));
         assert!(!help.contains("/login"));
         assert!(!help.contains("/logout"));
-        assert_eq!(slash_command_specs().len(), 139);
+        assert!(help.contains("/setup"));
+        assert_eq!(slash_command_specs().len(), 140);
         assert!(resume_supported_slash_commands().len() >= 39);
     }