fix: resolve GitHub Code scanning alerts #10 and #21 (#20)

## Summary
- Resolve GitHub Code scanning alert #10 (unreachable code warning)
- Resolve GitHub Code scanning alert #21 (mixed import style warning)
- Refactor test functions to improve code structure and maintainability

## Test plan
- [x] All 478 tests pass
- [x] Code formatting and style checks pass (ruff format, ruff check)
- [x] Type checking passes (mypy)
- [x] REUSE compliance check passes
- [x] Build verification successful (wheel and sdist)
- [x] All pre-commit hooks pass

## Changes Made

### Alert #10: Unreachable Code Warning
- **File**: `tests/test_unified_exception_handling.py`
- **Issue**: CodeQL detected unreachable code at line 455, caused by
static analyzer not understanding pytest.raises context manager control
flow
- **Solution**: Refactored
`test_error_handling_with_existing_py7zz_errors` function into four
separate test functions:
  - `test_file_not_found_error_raising`
  - `test_compression_error_raising`  
  - `test_extraction_error_raising`
  - `test_existing_py7zz_errors_inheritance`
- **Benefits**: Eliminates CodeQL warning, improves test readability and
structure, follows "one test, one concern" best practice

### Alert #21: Mixed Import Style Warning  
- **File**: `tests/test_pypi_version_validation.py`
- **Issue**: Mixed usage of `import py7zz` and `from py7zz.version
import ...` causing code style inconsistency
- **Solution**: Removed `from py7zz.version import ...` statement and
consistently use `py7zz.version.*` format
- **Benefits**: Consistent code style, clearer function origins, follows
Python best practices

## Technical Details
- All existing functionality preserved during refactoring
- Test coverage remains unchanged
- Full backward compatibility maintained
- Follows project code style conventions

## Verification
Complete CI simulation passed, including:
- Quick checks (format, lint, type checking)
- REUSE compliance verification  
- Build verification (wheel + sdist)
- Comprehensive test suite (478 tests)
- All pre-commit hooks

These fixes will automatically resolve the corresponding security alerts
in the next CodeQL scan.

Author: RxChi1d

scripts/quick-check.sh

@@ -265,25 +265,16 @@ def test_version_type_identification(self):
         assert parsed["version_type"] in ["stable", "alpha", "beta", "rc", "dev"]
 
         # Test version type functions
-        from py7zz.version import (
-            get_version_type,
-            is_alpha_version,
-            is_beta_version,
-            is_dev_version,
-            is_rc_version,
-            is_stable_version,
-        )
-
-        version_type = get_version_type(version)
+        version_type = py7zz.version.get_version_type(version)
         assert version_type in ["stable", "alpha", "beta", "rc", "dev"]
 
         # Test that exactly one version type function returns True
         type_checks = [
-            is_stable_version(version),
-            is_alpha_version(version),
-            is_beta_version(version),
-            is_rc_version(version),
-            is_dev_version(version),
+            py7zz.version.is_stable_version(version),
+            py7zz.version.is_alpha_version(version),
+            py7zz.version.is_beta_version(version),
+            py7zz.version.is_rc_version(version),
+            py7zz.version.is_dev_version(version),
         ]
         assert sum(type_checks) == 1, "Exactly one version type should be True"
 

tests/test_pypi_version_validation.py

@@ -446,19 +446,23 @@ def test_complex_error_context_tracking(self):
         assert info["context"]["progress"] == "3/5"
         assert len(info["suggestions"]) == 2
 
-    def test_error_handling_with_existing_py7zz_errors(self):
-        """Test error handling integration with existing py7zz error types."""
-        # Test that existing error types still work
+    def test_file_not_found_error_raising(self):
+        """Test that FileNotFoundError can be raised and caught properly."""
         with pytest.raises(py7zz.FileNotFoundError):
             raise py7zz.FileNotFoundError("test.txt")
 
+    def test_compression_error_raising(self):
+        """Test that CompressionError can be raised and caught properly."""
         with pytest.raises(py7zz.CompressionError):
             raise py7zz.CompressionError("Compression failed")
 
+    def test_extraction_error_raising(self):
+        """Test that ExtractionError can be raised and caught properly."""
         with pytest.raises(py7zz.ExtractionError):
             raise py7zz.ExtractionError("Extraction failed")
 
-        # Test that they're still Py7zzError instances
+    def test_existing_py7zz_errors_inheritance(self):
+        """Test that existing error types are still Py7zzError instances."""
         error = py7zz.CompressionError("Test")
         assert isinstance(error, py7zz.Py7zzError)