0.5.2 - Schema output and tool-calling go brrr for December

Added

• toolio.common.load_or_connect convenience function
• reddit_newsletter multi-agent demo

Changed

• Make the {json_schema} template "cutout" configurable, and change the default (to #!JSON_SCHEMA!#)

Fixed

• Clean up how optional dependencies are handled
• Tool-calling prompting enhancements
• Clean up HTTP client & server interpretation of tool-calling & schemata