common : Update the docs on -t --threads (#16236)

* Update the docs on -t --threads

* Revert "Update the docs on -t --threads"

This reverts commit eba97345e2c88d8ca510abec87d00bf6b9b0e0c2.

* docs: clarify -t/--threads parameter uses CPU threads and defaults to all available cores

* Update arg.cpp

common/arg.cpp

@@ -1760,7 +1760,7 @@ common_params_context common_params_parser_init(common_params & params, llama_ex
     ).set_examples({LLAMA_EXAMPLE_MAIN, LLAMA_EXAMPLE_SPECULATIVE, LLAMA_EXAMPLE_LOOKUP}));
     add_opt(common_arg(
         {"-t", "--threads"}, "N",
-        string_format("number of threads to use during generation (default: %d)", params.cpuparams.n_threads),
+        string_format("number of CPU threads to use during generation (default: %d)", params.cpuparams.n_threads),
         [](common_params & params, int value) {
             params.cpuparams.n_threads = value;
             if (params.cpuparams.n_threads <= 0) {