Design System — Onboarding + Shared Brand Tokens

The design-system skill is the shared brand owner for the markdown-html plugin. Run its onboarding once. Every converter (md-document, md-review, md-slides) reads the resulting config via config_loader.py and applies the same 12 CSS custom properties to its output. Without this, conversions render with placeholder defaults — technically functional but unbranded.

This skill ships exactly three Python tools:

1. onboard.py — interactive (or --defaults / --set / --show / --reset) wizard.
2. config_loader.py — importable customization loader with project > global > defaults precedence and MARKDOWN_HTML_NO_CONFIG=1 bypass.
3. brand_palette_validator.py — WCAG-AA contrast checker + HSL palette deriver.

All three are stdlib-only and contain no LLM calls (deterministic per Path-B discipline).

When to invoke

Symptom	Action
User says "convert this markdown to HTML" for the first time in this workspace	Run python3 markdown-html/skills/design-system/scripts/onboard.py
~/.config/markdown-html/design-system.json doesn't exist OR setup_completed_at is null	Refuse conversion, surface onboarding
User wants per-repo brand override	python3 .../onboard.py --scope project
User wants to change a single field non-interactively	python3 .../onboard.py --set brand.primary=#FF6B35
User wants to reset and re-onboard	python3 .../onboard.py --reset then re-run
User wants zero-touch defaults (CI, ephemeral session)	python3 .../onboard.py --defaults
Headless / containerized run that should ignore saved config	MARKDOWN_HTML_NO_CONFIG=1 ...

Onboarding question set (10 questions)

#	Key	Choices / Validator	Default
1	default_output_dir	path; os.access(parent, os.W_OK)	./markdown-html-out/
2	brand.primary	HEX ^#?[0-9a-fA-F]{6}$	#0A1628
3	brand.accent	HEX or blank (auto-derive)	derive from primary
4	typography.heading_font	Google Font name (12 safe defaults)	Inter
5	typography.body_font	Google Font name	Inter
6	design_style	editorial / technical / minimal / playful	technical
7	code_theme	light / dark / auto	auto
8	toc.behavior	sticky-sidebar / collapsible-top / inline / none	sticky-sidebar
9	company_name	string (may be empty)	""
10	logo_url	URL or empty (base64-embedded at render)	""

Hard rules

1. WCAG AA body-text contrast must pass. brand_palette_validator.validate() runs after every change. Body text on bg must reach 4.5:1; link on bg must reach 4.5:1. If either fails, onboard.py refuses to save (exit code 4) and tells the user to pick a darker primary, blank brand.bg/brand.text to let derivation pick a safe pair, or override brand.text directly. Canon: WCAG 2.2 §1.4.3.
2. Output directory must be writable. onboard.py walks up the path to find an existing ancestor and checks os.W_OK. Empty or unwritable path → exit code 3. The orchestrator's output_path_resolver.py honors the same rule per-conversion.
3. Customization must change behavior, not sit as decoration. Every consumer (md-document, md-review, md-slides) must read the config and render differently when the user changes design_style, brand.primary, code_theme, or toc.behavior. Decorative-only fields fail the design discipline.
4. Precedence is fixed. Project > global > defaults. The deep-merge preserves nested keys (e.g. you can override brand.primary in a project config without losing typography.heading_font from global).
5. Bypass env exists for a reason. MARKDOWN_HTML_NO_CONFIG=1 is for headless CI, ephemeral test containers, and the autoresearch-style evaluator loops. Never set it silently for an interactive user.

Derived 12-token palette

Once the user's brand is captured, brand_palette_validator.derive_palette() produces 12 CSS custom properties stored under derived_palette in the same config file. Every converter inlines these into its <style> block.

Token	Purpose	Derivation
--md-bg	Document background	Primary if dark, near-neutral if vibrant
--md-surface	Card / callout / blockquote background	Bg ± 4-6% luminance
--md-border	Hairline dividers, table borders	Bg ± 8-12% luminance
--md-text	Body text	Off-white on dark bg, near-black on light bg
--md-text-muted	Captions, metadata, footers	rgba(text, 0.68)
--md-accent	Primary CTA, callout headers, link emphasis	Primary if vibrant, hue-shifted lighter if dark
--md-accent-soft	Accent backgrounds, hover states	rgba(accent, 0.14)
--md-code-bg	Inline code, fenced block bg	Bg ± 4-5% luminance
--md-link	Hyperlinks	Iteratively walked to reach 4.5:1 contrast on bg
--md-link-hover	Hover state	Link ± 6-8% luminance
--md-success	OK / approved / passed	Green anchored, luminance-matched
--md-warn	Caution / nit / TODO	Amber anchored, luminance-matched

Forcing-question library (Matt Pocock grill-with-docs pattern)

One question per turn, recommended answer, canon citation.

1. What's your brand primary color? Recommended: a HEX you already use in your product or docs — not a stock blue. Canon: Aarron Walter, Designing for Emotion (color carries brand affect).
2. Should accent be derived or set? Recommended: derive on first run (hue-shift + lighten produces a coherent companion); set explicitly only if your brand kit specifies one. Canon: Adobe Spectrum, Color Foundations.
3. Editorial, technical, minimal, or playful? Recommended: technical for engineering specs/reports, editorial for long-read narratives, minimal for sparse reference docs, playful for marketing/landing content. Canon: Ellen Lupton, Thinking with Type (style serves the rhetorical purpose).
4. Sticky-sidebar TOC, or inline? Recommended: sticky-sidebar for documents over 800 words, inline for short reads. Canon: Nielsen-Norman, Table of Contents Best Practices (2023).
5. Save to global or per-project? Recommended: global by default (consistent across your work); use --scope project only when this repo has a different brand. Canon: research-ops onboarding pattern, research-ops/CLAUDE.md §8.

Customization in use (worked example)

# First-run onboarding (interactive, walks all 10 questions)
python3 markdown-html/skills/design-system/scripts/onboard.py

# Zero-touch defaults for CI / first-test
python3 .../onboard.py --defaults

# Change just the primary color and design style
python3 .../onboard.py --set brand.primary=#FF6B35 --set design_style=editorial

# Per-repo override
python3 .../onboard.py --scope project --set design_style=minimal

# Reset and re-onboard
python3 .../onboard.py --reset
python3 .../onboard.py

# Inspect the effective config (project > global > defaults)
python3 .../config_loader.py --show
python3 .../config_loader.py --status

# Bypass saved config (returns DEFAULTS only)
MARKDOWN_HTML_NO_CONFIG=1 python3 .../config_loader.py --show

# Spot-check WCAG contrast before committing to a brand
python3 .../brand_palette_validator.py --primary "#FF6B35" --accent "#00D4AA"

Assumptions

1. User has at least one brand HEX they want consistent across their HTML conversions.
2. User accepts a 1-2 minute one-time setup.
3. User is OK with Google Fonts as the typography source (CDN, no local font hosting).
4. WCAG 2.2 AA is the accessibility floor (4.5:1 body, 3:1 large/UI). AAA (7:1) is out of scope.

Non-goals

• Not a full design-token system (Style Dictionary, Theo). Twelve tokens, not a hundred.
• Not a custom-font hosting solution. Google Fonts only.
• Not a dark/light mode switcher in the converters. code_theme: auto handles the prefers-color-scheme case for syntax highlighting; layout palette is single-mode per onboarding.
• Not an accessibility audit suite (use axe-core / pa11y for that). We enforce contrast only.
• Does not transform existing CSS — the derived palette is injected into freshly generated HTML.

Distinct from

• marketing/landing/skills/landing/scripts/brand_palette_validator.py — that script's derive_palette() produces 8 tokens shaped for hero-page rendering (--navy, --teal, --card-bg, --card-border). This script produces 12 tokens shaped for document rendering (sticky surface, hairline border, code bg, link, link-hover, success, warn). Same WCAG + HSL math, different token taxonomy.
• research-ops/skills/clinical-research/scripts/onboard.py — same pattern (interactive + --defaults/--set/--show/--reset/--scope), different question set (clinical alpha/power/dropout vs. brand palette/typography/layout).

Output artifact

~/.config/markdown-html/design-system.json (global) or ./.markdown-html/design-system.json (project). JSON schema lives at assets/design_system_schema.json.

Anti-patterns (do not)

• ❌ Skip onboarding and run a converter with placeholder defaults — output looks unbranded.
• ❌ Pick a vibrant brand primary as brand.bg directly (low text contrast). Use it as accent instead.
• ❌ Set MARKDOWN_HTML_NO_CONFIG=1 silently for an interactive user — they'll wonder why their tokens disappeared.
• ❌ Encode brand semantics in derived_palette outside the 12-token taxonomy. Add a new token only with a deliberate name + purpose + derivation rule.

References

• WCAG 2.2 — §1.4.3 (contrast), §1.4.4 (resize), §1.4.11 (non-text contrast)
• Aarron Walter — Designing for Emotion (A Book Apart)
• Ellen Lupton — Thinking with Type
• Adobe Spectrum — Color Foundations
• Nielsen-Norman — Table of Contents Best Practices (2023)
• research-ops onboarding pattern: research-ops/CLAUDE.md §8
• Brand palette math source: marketing/landing/skills/landing/scripts/brand_palette_validator.py