Engineer's Notebook #10: The Design System You Can Actually Call

[Davidslv]

Draft — parked, not ready to publish.

Engineer's Notebook #10, adapted from the Compositor design-system write-up. Turns a twelve-chapter design-system manual into an invokable Rails component library.

What it covers

• The decision: strict-locals partials + helpers vs ViewComponent vs Phlex — and why partials won for this codebase (portability, the Herb+RuboCop gate, day-one onboarding).
• The non-isolated compositor engine and the strict-locals + **attrs pairing.
• The preview-driven registry that auto-wires every helper and a self-discovering guide — so docs can't drift from code.
• The 22-component fan-out and how the gates caught the bugs it introduced.

Scheduling / safety

• Dated 2026-06-25. future: false in _config.yml keeps it off the live site until that date, so merging early won't publish it prematurely.
• Cross-links the previous entry (AI development reality check article #9, the Herb/view-layer post).
• House convention honoured: no "Quire" product name in prose; code identifiers only.

Notes for review

• Adapted from an internal doc; dropped a dead internal link and reframed the intro for the series voice.
• Homepage/writing index will feature this as "Latest" once it's no longer future-dated.