Only run Input Validator on .in files in data

spec/2025-09.md

@@ -958,8 +958,8 @@ Input validators can be written in three formats: as a program (as specified [ab
 a [VIVA](http://viva.vanb.org/)-file (with file ending `.viva`), 
 or a [Checktestdata](https://github.com/DOMjudge/checktestdata)-file (with file ending `.ctd`).
 
-Every input validator will be run on every test case defined in `data`, as well as on any `nextpass.in` files that are dynamically generated during the execution of a `multi-pass` problem.
-Validation fails if any validator fails. It is a judge error for validation of a `nextpass.in` file to fail.
+Every input validator will be run on every test case defined in `data`.
+Validation fails if any validator fails.
 
 ### Invocation
 
@@ -970,13 +970,10 @@ The validator should be possible to use as follows on the command line:
 <input_validator_program> [arguments] < inputfile
 ```
 
-- `inputfile` is either a `.in` file defined in the `data` directory, or a `nextpass.in` file generated by an output validator.
+- `inputfile` is a `.in` file defined in the `data` directory.
 - `arguments` are the `input_validator_args` followed by the `args` of the testcase being validated. They must be chosen such that the input validator can distinguish which arguments belong to `input_validator_args`, and which belong to `args`. 
 - All files from `.files` will be copied into the input validtor's working directory for validation, see [Working directory](#working-directory).
 
-If `inputfile` is a `nextpass.in` file, the `.files`, `.args` and `input_validator_args` from the `.in` file used in the
-first pass will be used.
-
 ### Output
 
 The input validator may output debug information on stdout and stderr.