* cli: The family of error messages with the summary "Invalid for_each argument" will now include some additional context about which external values contributed to the result. [GH-26747]
* cli: Exit with an error if unable to gather input from the UI. For example, this may happen when running in a non-interactive environment but without `-input=false`. Previously Terraform would interpret these errors as empty strings, which could be confusing. [GH-26509]