fix: fix CONTRIBUTING.md placeholders, bare except clauses, and add convert.py tests (#3485) [skip ci]

* docs: fix codestyle placeholders in CONTRIBUTING.md

Replace unresolved {codestyle} and {URLofCodestyle} template
variables with Ruff, the project's actual linter/formatter
as configured in .pre-commit-config.yaml.

* fix: replace bare except clauses with specific exception types

- quantization.py: use except ImportError for optional torchao imports
  (consistent with line 48 which already uses ImportError correctly)
- cli/config.py: use except (RuntimeError, AssertionError) for CUDA
  device property query

Prevents masking unrelated errors like KeyboardInterrupt or SystemExit.

* test: add unit tests for convert.py JSON/JSONL utilities

Cover FileReader, FileWriter, StdoutWriter, JsonParser,
JsonlSerializer, and JsonToJsonlConverter with 8 test cases
including roundtrip and edge case (empty list) scenarios.

Previously this module had zero test coverage.

* fix: address CodeRabbit review feedback

- quantization.py: catch (ImportError, RuntimeError) for optional
  torchao imports; CUDA wheel/GPU mismatches raise RuntimeError,
  not ImportError
- convert.py: remove unused output_file_path parameter from
  JsonToJsonlConverter.convert() — FileWriter already holds the
  output path from construction
- tests/test_convert.py: update call site to match new signature

src/axolotl/cli/config.py

@@ -300,7 +300,7 @@ def load_cfg(
     try:
         device_props = torch.cuda.get_device_properties("cuda")
         gpu_version = "sm_" + str(device_props.major) + str(device_props.minor)
-    except:
+    except (RuntimeError, AssertionError):
         gpu_version = None
 
     prepare_plugins(cfg)

src/axolotl/convert.py

@@ -67,7 +67,7 @@ class JsonToJsonlConverter:
         self.json_parser = json_parser
         self.jsonl_serializer = jsonl_serializer
 
-    def convert(self, input_file_path, output_file_path):
+    def convert(self, input_file_path):
         content = self.file_reader.read(input_file_path)
         data = self.json_parser.parse(content)
         # data = [r for r in data if r["conversations"]]  # vicuna cleaned has rows with empty conversations

src/axolotl/utils/quantization.py

@@ -29,7 +29,7 @@ if version.parse(torch.__version__) >= version.parse("2.8.0"):
         from torchao.prototype.mx_formats import NVFP4InferenceConfig
 
         quantization_config_to_str[NVFP4InferenceConfig] = "nvfp4"
-    except:
+    except (ImportError, RuntimeError):
         pass
 
     # int4 weight config imports will fail on machines with fbgemm-gpu installed
@@ -38,7 +38,7 @@ if version.parse(torch.__version__) >= version.parse("2.8.0"):
         from torchao.quantization.quant_api import Int4WeightOnlyConfig
 
         quantization_config_to_str[Int4WeightOnlyConfig] = "int4"
-    except:
+    except (ImportError, RuntimeError):
         pass
 
     try: