Migration from __meta_design__ to __design__ in __pinjected__.py

[proboscis]

---\nMigrated from CyberAgentAILab/pinjected#3\nOriginally created by @app/devin-ai-integration on null\n\n---\n\n## Background
The framework is migrating from __meta_design__ to __design__ in __pinjected__.py as the preferred way to configure dependencies.

Current Status

• Warning logs have been added to alert users when __meta_design__ is found (PR Make create_configuration hookable to support multiple runtime configurations #2)
• The a_gather_from_path method is already marked as deprecated in favor of a_gather_bindings_with_legacy

Tasks

• Create comprehensive migration guide documentation
• Add automated migration tool/script to help users convert existing __meta_design__ to __design__ in __pinjected__.py
• Meta files for package #9
• Consider adding deprecation timeline for complete removal of __meta_design__ support

Related

• PR Make create_configuration hookable to support multiple runtime configurations #2: Add warning logs for __meta_design__ usage

Requested by: masui_kento@cyberagent.co.jp