perf(load): use libyaml CLoader when available

Base the TUM loaders (and the param-file load) on yaml.CLoader when
PyYAML is built with libyaml, falling back to the pure-Python Loader
otherwise. Same ParserError/ScannerError, same custom !include
constructors. YAML parse time ~8x lower; validation suite identical
(same verdicts, same 8 expected-fail tracebacks, post-exec SUCCESS).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/testium/interpreter/utils/include.py

@@ -6,10 +6,10 @@ from runtime.tum_except import ETUMFileError
 from interpreter.utils.template import template_to_test
 from copy import copy
 from interpreter.utils.globdict import global_dict
-from interpreter.utils.yaml_load import yaml_load
+from interpreter.utils.yaml_load import yaml_load, YAML_BASE_LOADER
 
 
-class TUMLoaderNoIncludes(yaml.Loader):
+class TUMLoaderNoIncludes(YAML_BASE_LOADER):
 
     def __init__(self, stream):
 

src/testium/interpreter/utils/test_init.py

@@ -11,7 +11,7 @@ import api.testium as tm
 import interpreter.utils.globdict as globdict
 import interpreter.utils.settings as prefs
 from interpreter.utils.paths import testium_path
-from interpreter.utils.yaml_load import yaml_load
+from interpreter.utils.yaml_load import yaml_load, YAML_BASE_LOADER
 from interpreter.utils import clear_recursively
 from runtime.tum_except import ETUMSyntaxError
 from interpreter.utils.params import expanse, eval_func_init
@@ -89,7 +89,7 @@ def locate_report_file(rep_file):
 def yamltodict(param_file, silent=True):
     # load of the file
     with open(param_file, "r") as fd:
-        dp = yaml_load(fd, param_file, yaml.Loader)
+        dp = yaml_load(fd, param_file, YAML_BASE_LOADER)
 
     if dp is None:
         tm.print_info(f"The YAML file '{param_file}' is empty.")

src/testium/interpreter/utils/yaml_load.py

@@ -1,3 +1,4 @@
+import yaml
 from yaml.parser import ParserError
 from yaml import load, Loader
 from yaml.scanner import ScannerError
@@ -5,6 +6,12 @@ from api.testium import print_debug
 from runtime.tum_except import ETUMSyntaxError
 import io
 
+# Use the libyaml-backed loader (much faster parsing) when PyYAML was built
+# with it, falling back to the pure-Python loader otherwise. The C loader
+# raises the same ParserError/ScannerError and supports the same custom
+# constructors (!include) and construct_* helpers the TUM loaders rely on.
+YAML_BASE_LOADER = yaml.CLoader if getattr(yaml, "__with_libyaml__", False) else yaml.Loader
+
 
 def print_yaml(file: io.TextIOWrapper, file_name):
     """ Prints YAML file if debug mode is activated.