- Remove import json (not needed, using msgspec for everything)
- Keep imports clean and minimal

## Tests (22 test cases)
- ✅ Basic settings creation with defaults
- ✅ Environment variable loading and type conversion
- ✅ Boolean conversion (true/false/1/0/yes/no variants)
- ✅ Environment prefixes (env_prefix)
- ✅ .env file loading
- ✅ Optional fields (str | None)
- ✅ Complex types (lists, dicts from JSON env vars)
- ✅ Validation errors (missing required, wrong types)
- ✅ Case sensitivity handling
- ✅ model_dump(), model_dump_json(), schema() methods
- ✅ Struct instance verification
- ✅ Class caching
- ✅ Env var priority (defaults < env < explicit)

## Examples (5 practical examples)
1. **01_basic_usage.py** - Fundamentals of settings management
2. **02_env_prefix.py** - Using env_prefix for namespacing
3. **03_dotenv_file.py** - Loading from .env files
4. **04_advanced_types.py** - Complex types (Optional, lists, dicts)
5. **05_serialization.py** - Serialization and schema generation

Each example includes:
- Runnable code with clear output
- Best practices and tips
- Real-world use cases

## Test Coverage
All core functionality tested:
- Environment loading ✓
- Type conversion ✓
- Validation ✓
- Serialization ✓
- Edge cases ✓

All tests pass: 22/22 ✅
All examples run successfully ✅

## Performance Optimizations

### 1. Cached Encoders and Decoders
- Reuse `msgspec.json.Encoder` and `msgspec.json.Decoder` instances
- Avoid repeated instantiation overhead
- `_encoder_cache` and `_decoder_cache` as class variables

### 2. Automatic Field Ordering
- Required fields now automatically placed before optional fields
- Prevents "Required field cannot follow optional fields" error
- Safer and more robust struct creation

### 3. Fixed Optional Type Bug
- Corrected Union type detection logic
- Changed from `origin is type(None)` (never true) to `origin is Union`
- Properly unwraps `Optional[T]` → `Union[T, NoneType]` → `T`
- Example: `Optional[int]` now correctly detected and unwrapped

## Code Quality

- Added `Union` import from typing
- Improved error handling with chained exceptions
- Better comments explaining the optimizations

## Testing

- ✅ All 22 tests pass
- ✅ Tests run 2x faster (0.10s → 0.05s)
- ✅ Benchmark maintains performance: 0.702ms per load
- ✅ Examples still work correctly

## Technical Details

**Before (Union bug):**
```python
origin = get_origin(field_type)
if origin is type(None) or origin is type(int | None):  # Never true!
    ...
```

**After (correct):**
```python
origin = get_origin(field_type)
if origin is Union:  # Correctly detects Optional[T]
    args = get_args(field_type)
    non_none_types = [a for a in args if a is not type(None)]
    if len(non_none_types) == 1:
        field_type = non_none_types[0]
```

**Field ordering:**
```python
# Before: Mixed order could cause errors
fields = [(name, type, default), ...]

# After: Required first, then optional
required_fields = [(name, type), ...]
optional_fields = [(name, type, default), ...]
fields = required_fields + optional_fields
```

These optimizations make the code more robust while maintaining peak performance.

- Updated benchmark from 0.933ms to 0.702ms (33% improvement)
- msgspec-ext now 3.8x faster than pydantic-settings (was 2.9x)
- Added key optimizations list to performance section
- Updated comparison table with new performance numbers
- Changed Python version reference from 3.13 to 3.12 (actual test env)

- Remove dynaconf from benchmark comparisons (not used)
- Remove unused imports (tempfile, Path)
- Update docstring to reflect current comparisons
- Add .benchmarks/ to gitignore (pytest-benchmark cache directory)
- Simplify benchmark output to focus on msgspec-ext vs pydantic

- Add ClassVar annotations for class-level caches
- Import ClassVar from typing
- Fix docstring formatting (D212)
- Remove unused _apply_defaults method
- All checks pass for src/ directory

Lint results:
- Before: 4 errors in src/
- After: 0 errors (all checks passed)

All 22 tests still passing ✅

- Add S104 (binding to all interfaces) ignore for examples/tests
- Add F401 (unused imports) ignore for examples/tests
- Add PLC0415 (top-level import) ignore for tests
- Run ruff format on all files (3 files reformatted)
- Update pyproject.toml per-file-ignores

All checks now pass ✅
All 22 tests passing ✅