Document secure workstation setup and slow terminal scroll

[ZILECAO]

Summary

• reduce terminal wheel and trackpad scrolling to one-fifth speed while keeping the Alt fast-scroll path at normal xterm speed
• add a public-safe workstation guide and $setup-agentformation skill for AWS CLI Identity Center sign-in, Docker Buildx, and macOS/Linux plus amd64/arm64 detection
• clarify that AWS account permission sets and AgentFormation application assignments control different access
• prevent AWS credential caches and platform-specific binaries from entering agent-config migrations

Security and privacy

• recommends temporary IAM Identity Center credentials instead of root or static access keys
• adds no AWS credentials, account identifiers, company addresses, deployment state, or deployment automation
• makes no IAM, CloudFormation, or other infrastructure change

Validation

• ./scripts/check.sh (48 tests, audit, formatting, lint, types, production build, ShellCheck, and CloudFormation lint)
• both repository skills pass quick_validate.py
• changed root docs and skill metadata pass Prettier
• staged diff checked for private company identifiers

AWS resources and cost

None. The web scroll change takes effect only after a normal maintainer web deployment.