Prevent processing of zero-byte config payloads

[jkebinger]

Summary

Add validation to reject zero-byte config payloads from both HTTP and SSE endpoints, treating them as connection errors that trigger retry logic.

Problem

The SDK could potentially attempt to process empty config data, which would likely cause parsing errors or unexpected behavior.

Solution

• Added zero-byte validation in config_sdk.py for HTTP responses
• Added zero-byte validation in _sse_connection_manager.py for SSE events
• When zero-byte payloads are detected:
  • HTTP: Returns False to trigger fallback/retry logic
  • SSE: Returns early to trigger reconnection logic
• Logs warning messages when zero-byte payloads are encountered

Testing

• Added comprehensive test coverage for both HTTP and SSE scenarios
• Tests verify that zero-byte payloads are properly rejected
• Tests verify that valid payloads continue to work normally
• All existing tests continue to pass

🤖 Generated with Claude Code

[jdwyah]

thanks