docs: complete Storage package docs for v3.0

[armanist]

Summary

• updated v3.0/packages/storage/usage.md
• updated v3.0/packages/storage/contracts.md
• updated v3.0/packages/storage/architecture.md
• updated v3.0/packages/storage/adapters.md

Coverage

• completed the Storage revisit pass for upload staging, remote adapter usage, and Google Drive placement guidance

Notable contracts

• documented that UploadedFile::save() still stages reads through the local adapter before remote writes
• documented the non-HTTP source copy path used in tests and CLI flows
• documented Google Drive parent-folder placement guidance through adapter-level put(..., $parentId) calls