docs(design): add DESIGN.md design system documentation

[jd]

Depends-On: #11301

[jd]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	feat(design): add primitive token layer (tokens.css)	#11299
2	feat(design): add typography utilities (typography.css)	#11300
3	feat(design): load tokens.css and typography.css	#11301
4	docs(design): add DESIGN.md design system documentation	#11302	👈
5	docs(design): link DESIGN.md from AGENTS.md and CLAUDE.md	#11303
6	fix(lint): exclude root *.md files from remark-lint rules	#11304
7	fix(design): address Phase 1 code review findings	#11305
8	refactor(design): map semantic tokens to new primitive layer	#11307
9	fix(header): solid distinct navbar surface for light-mode readability	#11308
10	refactor(design): migrate CommunityButton and CopyForLLMButton off Chakra	#11319
11	refactor(design): migrate Button.astro off Chakra ramps	#11320
12	refactor(design): replace Chakra inline styles in merge-queue.mdx	#11321
13	refactor(design): align MDX heading rules with typography utilities	#11322
14	refactor(design): migrate homepage to typography utility classes	#11323
15	refactor(design): align expressive-code overrides with semantic tokens	#11324
16	refactor(design): remove Chakra color block	#11325
17	fix(design): address Phase 3 code review findings	#11326
18	refactor(design): collapse per-section accent rules into single tokenized rule	#11328
19	refactor(design): tokenize home-discovery callout (placeholder for B)	#11329
20	refactor(design): migrate --color-mergify-blue consumers to semantic tokens	#11330
21	refactor(design): remove --color-mergify-blue and HSLA primitives	#11331
22	fix(design): migrate orphan --theme-dim* and --theme-text-accent refs	#11332
23	fix(design): address Phase 4 code review findings	#11333
24	fix(layout): remove left-sidebar rounded scoop	#11334

[mergify]

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🔴 ⛓️ Depends-On Requirements

Waiting for:

• depends-on = Mergifyio/docs#11299 [⛓️ feat(design): add primitive token layer (tokens.css) #11299 [stack]]
• depends-on = Mergifyio/docs#11300 [⛓️ feat(design): add typography utilities (typography.css) #11300 [stack]]
• depends-on = Mergifyio/docs#11301 [⛓️ feat(design): load tokens.css and typography.css #11301 [stack]]

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Requirement based on the presence of Depends-On in the body of the pull request

• depends-on = Mergifyio/docs#11299 [⛓️ feat(design): add primitive token layer (tokens.css) #11299 [stack]]
• depends-on = Mergifyio/docs#11300 [⛓️ feat(design): add typography utilities (typography.css) #11300 [stack]]
• depends-on = Mergifyio/docs#11301 [⛓️ feat(design): load tokens.css and typography.css #11301 [stack]]

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• body ~= (?ms:.{48,})

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• body ~= (?ms:.{48,})

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• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert|ui)(?:\(.+\))?:

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• #changes-requested-reviews-by = 0
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[jd]

Revision history

#	Type	Changes	Reason	Date
1	initial	e2a3911		2026-04-29 13:21 UTC
2	rebase	e2a3911 → 9907718		2026-04-29 13:21 UTC
3	rebase	9907718 → baa14d8		2026-04-30 07:56 UTC
4	rebase	baa14d8 → f16ff9e		2026-04-30 09:12 UTC