docs(design): add shared design source (#3507)

* docs(design): add shared design source

* fix(design): use https design submodule url

* docs(design): update agent design references

Author: Drixled

.gitmodules

@@ -0,0 +1,3 @@
+[submodule ".kilo/design"]
+	path = .kilo/design
+	url = https://github.com/Kilo-Org/kilo-design.git

.kilo/design

@@ -37,7 +37,7 @@ Target a specific test file: `pnpm test -- <path>`. Run tests for a specific ser
 
 ## apps/web UI Work
 
-Before making or reviewing UI changes under `apps/web` — components, routes/pages, layouts, styling, Storybook, visual polish, UX copy, interaction states, responsive behavior, theming, or accessibility — read `design.md` and use `.agents/skills/kilo-design/SKILL.md`. This applies even when the prompt does not explicitly mention design. Skip only for backend-only or non-visual logic changes.
+Before making or reviewing UI changes under `apps/web` — components, routes/pages, layouts, styling, Storybook, visual polish, UX copy, interaction states, responsive behavior, theming, or accessibility — read `DESIGN.md` and use `.agents/skills/kilo-design/SKILL.md`. This applies even when the prompt does not explicitly mention design. Skip only for backend-only or non-visual logic changes.
 
 ## Coding Standards
 

AGENTS.md

@@ -0,0 +1,17 @@
+# Kilo Cloud Design
+
+Canonical design source is vendored into this repo as a Git submodule:
+
+```txt
+.kilo/design
+```
+
+Read in order:
+
+1. `.kilo/design/DESIGN.md`
+2. `.kilo/design/products/cloud.md`
+3. `.kilo/design/tokens.json`
+
+Do not add independent design rules in this repo. Promote design changes back to `kilo-design`, then update product implementation here.
+
+Update the `.kilo/design` submodule pointer when canonical design guidance changes.

DESIGN.md

@@ -4,7 +4,7 @@
 
 When doing UI work in `apps/web` — including React components, routes/pages, layouts, styling, Storybook stories, visual polish, UX copy, interaction states, responsive behavior, theming, or accessibility — you must:
 
-1. Read `../../design.md` before changing or reviewing UI.
+1. Read `../../DESIGN.md` before changing or reviewing UI.
 2. Load and follow the `kilo-design` skill at `../../.agents/skills/kilo-design/SKILL.md`.
 3. Prefer existing Kilo tokens, components, and utilities before adding new visual primitives.