One pixel-grid identity: the livery package, its generator, and the drift-gated SVG assets

Summary

spc-36 delivers itd-133's visual identity as data plus derivation: a new internal/livery package holds the canonical pixel grids for all seven assets (duckling full and mini; signal-flag logo full, compact, and the 2×2 icon arrangement — two flags per row, naturally square, the app/web icon candidate, maintainer-requested 2026-08-21; lifeboat full and mini) and their palette; a Go generator derives the committed SVG assets from those grids; and a package test regenerates the SVGs on every go test run and fails on any byte difference. No terminal rendering ships here — itd-112 consumes the grids later. No forge page is rewired — docs/assets/img/ logo.png remains the forge/web logo.

The package is named livery — a vessel's livery is its distinctive colours and markings — deliberately avoiding a third homonym on "identity" (the git-author gate and the positioning block already share nothing but the word), which resolves the intent's third open question.

Scope

In: internal/livery (grids, palette, SVG derivation), a go:generate program writing docs/assets/img/livery/*.svg — seven assets × two canvases (natural, and square for avatar/icon use; maintainer-requested 2026-08-21) × two variants (panel, transparent), 28 files — the in-sync test, geometry tests, a CHANGELOG entry.

Out (per the intent): ANSI/terminal rendering, colour detection, fallbacks (itd-112); README/web changes; identity-block schema changes.

Approach

• Grids as Go source. Each asset is a []string of single-character cells (one colour key per cell) in internal/livery/grids.go, with the palette as a map[rune] of hex colours. Exported read-only accessors give itd-112 its future input. A well-formedness test asserts every row of a grid has equal width and every cell is palette-known.
• Generator. internal/livery/gen is a small program invoked via go generate ./internal/livery/...; it renders each grid to SVG (<rect> per cell, shape-rendering="crispEdges") in two variants: panel (rounded dark panel behind the art — legible on any background) and transparent (dark surfaces only; its <desc> says so), each on two canvases: natural, and square with the art centered (the side is the larger natural dimension, so nothing is cropped or scaled; the <desc> labels it for avatar and icon use). The compact logo's SVG carries a <desc> stating its geometry is approximate, and the grids' doc comments repeat both labels. Output is deterministic (fixed ordering, no timestamps), which is what makes the drift gate byte-exact.
• Drift gate as a test. TestSVGAssetsInSync renders every variant in-memory and byte-compares against the committed files under docs/assets/img/livery/, failing with the asset name on mismatch. Living in go test ./..., it runs in make preflight and both CI legs with no new workflow step.
• Geometry as a test. TestFlagGeometry asserts the full-size flag grids against the ICS patterns: alfa vertically halved white/blue with a swallowtail notch, bravo all-red with a swallowtail notch, charlie's five horizontal stripes blue-white-red-white-blue, delta's three bands yellow-blue-yellow. The same assertions run over the icon arrangement's four flags at their 2×2 offsets. The compact grid is exempt by design and asserted only to carry its approximate label.

Acceptance criteria → how satisfied

1. One canonical definition, no second copy — the grids exist only in internal/livery/grids.go; the SVGs are generated from them and the in-sync test proves derivation; the scratch prototypes stay untracked and unreferenced.
2. Byte-identical regeneration — TestSVGAssetsInSync, running in preflight and CI.
3. Legible light and dark — panel variants carry their own background; transparent variants are labelled dark-surface-only in their <desc> and doc comments; no forge page rewiring.
4. True geometry full-size, labelled-approximate compact — TestFlagGeometry plus the compact variant's labels.
5. Role assignment discoverable — recorded in dcn-2608210000000002 (2026-08-21 entry), linked from the intent's Prior Art and criteria.
6. Ships via docs/, scratch stays local — assets land under docs/assets/img/livery/, already inside the launch payload's docs/ inclusion; the bundler's namespace denial keeps .abcd/** out structurally; no committed file references the local tier.

Notes

The SVG palette is the 256-colour-mode palette's hex equivalents (terracotta #d97757, yellow #f0c052, red #cf554d, blue #4a6fb5, water #2b7a8c, gold #d9a441, white #e8e8e8, mast grey #9aa0a8, panel #1c1f26); when itd-112 builds terminal rendering it maps the same palette keys to ANSI, so the grids stay the single source across both pipelines.