formatAddonWarning

Render an AddonWarning to a developer-friendly message.

Returns the bare message — the [Dynamic Forms] prefix is added by the library's logger (ConsoleLogger) and by DynamicFormError. Pass the result of this function directly into logger.warn(...) to get the standard prefixed line; use logAddonWarnings() for direct console.warn output (which prefixes manually).

Messages are designed to be actionable: they enumerate the relevant set (registered kinds, allowed slots) and suggest a likely fix.