feat: Add bucket management APIs and improve SDK filtering

This commit adds core bucket management functionality and enhances the SDK's internal file filtering to provide a cleaner abstraction layer.

**Bucket Management**:
- Add create_bucket(), delete_bucket(), list_buckets() to DeltaGliderClient
- Idempotent operations (creating existing bucket or deleting non-existent returns success)
- Complete boto3-compatible API for basic bucket operations
- Eliminates need for boto3 in most use cases

**Enhanced SDK Filtering**:
- SDK now filters .delta suffix and reference.bin from all list_objects() responses
- Simplified CLI to rely on SDK filtering (removed duplicate logic)
- Single source of truth for internal file hiding

**Delete Cleanup Logic**:
- Automatically removes orphaned reference.bin when last delta in DeltaSpace is deleted
- Prevents storage waste from abandoned reference files
- Works for both single delete() and recursive delete_recursive()

**Documentation & Testing**:
- Added BOTO3_COMPATIBILITY.md documenting actual 20% method coverage (21/100+ methods)
- Updated README to reflect accurate boto3 compatibility claims
- New comprehensive test suite for filtering and cleanup features (test_filtering_and_cleanup.py)
- New bucket management test suite (test_bucket_management.py)
- Example code for bucket lifecycle management (examples/bucket_management.py)
- Fixed mypy configuration to eliminate source file found twice errors
- All CI checks passing (lint, format, type check, 18 unit tests, 61 integration tests)

**Cleanup**:
- Removed PYPI_RELEASE.md (redundant with existing docs)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

pyproject.toml

@@ -144,8 +144,12 @@ disallow_untyped_defs = true
 disallow_any_unimported = false
 no_implicit_optional = true
 check_untyped_defs = true
-namespace_packages = true
-explicit_package_bases = true
+namespace_packages = false
+mypy_path = "src"
+exclude = [
+    "^build/",
+    "^dist/",
+]
 
 [tool.pytest.ini_options]
 minversion = "8.0"