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>

examples/bucket_management.py

@@ -0,0 +1,116 @@
+#!/usr/bin/env python3
+"""Example: Bucket management without boto3.
+
+This example shows how to use DeltaGlider's bucket management APIs
+to create, list, and delete buckets without needing boto3 directly.
+"""
+
+from deltaglider import create_client
+
+# Create client (works with AWS S3, MinIO, or any S3-compatible storage)
+client = create_client()
+
+# For local MinIO/S3-compatible storage:
+# client = create_client(endpoint_url='http://localhost:9000')
+
+print("=" * 70)
+print("DeltaGlider Bucket Management Example")
+print("=" * 70)
+
+# 1. List existing buckets
+print("\n1. List all buckets:")
+try:
+    response = client.list_buckets()
+    if response["Buckets"]:
+        for bucket in response["Buckets"]:
+            print(f"  - {bucket['Name']} (created: {bucket.get('CreationDate', 'unknown')})")
+    else:
+        print("  No buckets found")
+except Exception as e:
+    print(f"  Error: {e}")
+
+# 2. Create a new bucket
+bucket_name = "my-deltaglider-bucket"
+print(f"\n2. Create bucket '{bucket_name}':")
+try:
+    response = client.create_bucket(Bucket=bucket_name)
+    print(f"  ✅ Created: {response['Location']}")
+except Exception as e:
+    print(f"  Error: {e}")
+
+# 3. Create bucket with region (if using AWS)
+# Uncomment for AWS S3:
+# print("\n3. Create bucket in specific region:")
+# try:
+#     response = client.create_bucket(
+#         Bucket='my-regional-bucket',
+#         CreateBucketConfiguration={'LocationConstraint': 'us-west-2'}
+#     )
+#     print(f"  ✅ Created: {response['Location']}")
+# except Exception as e:
+#     print(f"  Error: {e}")
+
+# 4. Upload some files to the bucket
+print(f"\n4. Upload files to '{bucket_name}':")
+try:
+    # Upload a simple file
+    client.put_object(
+        Bucket=bucket_name,
+        Key="test-file.txt",
+        Body=b"Hello from DeltaGlider!",
+    )
+    print("  ✅ Uploaded: test-file.txt")
+except Exception as e:
+    print(f"  Error: {e}")
+
+# 5. List objects in the bucket
+print(f"\n5. List objects in '{bucket_name}':")
+try:
+    response = client.list_objects(Bucket=bucket_name)
+    if response.contents:
+        for obj in response.contents:
+            print(f"  - {obj.key} ({obj.size} bytes)")
+    else:
+        print("  No objects found")
+except Exception as e:
+    print(f"  Error: {e}")
+
+# 6. Delete all objects in the bucket (required before deleting bucket)
+print(f"\n6. Delete all objects in '{bucket_name}':")
+try:
+    response = client.list_objects(Bucket=bucket_name)
+    for obj in response.contents:
+        client.delete_object(Bucket=bucket_name, Key=obj.key)
+        print(f"  ✅ Deleted: {obj.key}")
+except Exception as e:
+    print(f"  Error: {e}")
+
+# 7. Delete the bucket
+print(f"\n7. Delete bucket '{bucket_name}':")
+try:
+    response = client.delete_bucket(Bucket=bucket_name)
+    print(f"  ✅ Deleted bucket (status: {response['ResponseMetadata']['HTTPStatusCode']})")
+except Exception as e:
+    print(f"  Error: {e}")
+
+# 8. Verify bucket is deleted
+print("\n8. Verify bucket deletion:")
+try:
+    response = client.list_buckets()
+    bucket_names = [b["Name"] for b in response["Buckets"]]
+    if bucket_name in bucket_names:
+        print(f"  ❌ Bucket still exists!")
+    else:
+        print(f"  ✅ Bucket successfully deleted")
+except Exception as e:
+    print(f"  Error: {e}")
+
+print("\n" + "=" * 70)
+print("✅ Bucket management complete - no boto3 required!")
+print("=" * 70)
+
+print("\n📚 Key Benefits:")
+print("  - No need to import boto3 directly")
+print("  - Consistent API with other DeltaGlider operations")
+print("  - Works with AWS S3, MinIO, and S3-compatible storage")
+print("  - Idempotent operations (safe to retry)")