tools/nxstyle: add a script to check a whole tree at once

nxstyle checks one file per invocation.  nxstyle_sweep.sh runs it over
the directories given, or the whole repository, and collects what it
reports.

Signed-off-by: raiden00pl <raiden00@railab.me>
Assisted-by: Claude Code

Documentation/components/tools/nxstyle_sweep.rst

@@ -0,0 +1,25 @@
+====================
+``nxstyle_sweep.sh``
+====================
+
+Run ``nxstyle`` over whole directories, or over the repository, and collect
+what it reports. Usage:
+
+.. code:: console
+
+   $ tools/nxstyle_sweep.sh [options] [<dir> ...]
+
+     -o <file>   Diagnostics                (default: nxstyle-errors.txt)
+     -f <file>   Failing files, worst first (default: nxstyle-files.txt)
+     -l          List failing files instead of writing the reports
+     -s          Summarise the diagnostics by message
+     -b <path>   Use an existing nxstyle binary
+     -j <n>      Number of parallel checks
+     -a          Check every file, not only those tracked by git
+     -h          Show this help
+
+Options must precede the directories, which default to the whole repository
+and are relative to its top. The exit status is non-zero if anything was
+reported.
+
+See also ``nxstyle``.