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

.github/CONTRIBUTING.md

@@ -68,7 +68,7 @@ You can skip certain CI checks by including specific keywords in your commit mes
 
 ### Code Style
 
-axolotl uses [{codestyle}]({URLofCodestyle}) as its code style guide. Please ensure that your code follows these guidelines.
+axolotl uses [Ruff](https://docs.astral.sh/ruff/) as its code style guide. Please ensure that your code follows these guidelines.
 
 Use the pre-commit linter to ensure that your code is formatted consistently.
 ```bash
@@ -83,6 +83,6 @@ Write clear and concise commit messages that briefly describe the changes made i
 
 - [GitHub Help](https://help.github.com/)
 - [GitHub Pull Request Documentation](https://docs.github.com/en/github/collaborating-with-issues-and-pull-requests)
-- [{codestyle}]({URLofCodestyle})
+- [Ruff](https://docs.astral.sh/ruff/)
 
 Thank you once again for your interest in contributing to axolotl. We look forward to collaborating with you and creating an even better project together!