Improve Codebase Architecture

Read the Stacks adaptation rules, then
PLAYBOOK.md. The playbook preserves this workflow's decision
criteria; the Stacks rules govern APIs, tooling, tracking, and authorization.

Credit: adapted from Matt Pocock's improve-codebase-architecture skill, MIT licensed.
See NOTICE.md and LICENSE.

Completion

Produce the requested behavior or reviewable artifact and satisfy the
playbook's completion criteria. Preserve existing decisions and user edits.
Use the native Stacks skills for implementation and verification, and carry
existing authorization through the workflow.