Add durable image input and game perception

[EricSun0218]

Summary

• add bounded, content-addressed image attachments for in-process and server runtimes
• persist image references and resolve bytes only after model capability preflight
• expose secure JSON/SSE and authorized attachment reads
• package the feature for Godot, Unity, and server deployments
• document the recommended structured-state + sparse spatial view + selective-image perception stack

Validation

• 874 Release tests
• Release build and format gates
• Godot 4.7.1 .NET editor smoke
• Unity 6000.5.6f1 editor smoke
• release script and public-tree gates