chore: designate AGENTS.md as single source of truth for AI configs

Reduce duplication by keeping only compact rule bullets in .cursorrules
and copilot-instructions.md, with a reference to AGENTS.md for full
examples and detailed standards.

Author: kimyouknow

.cursorrules

@@ -1,13 +1,15 @@
 # react-simplikit Cursor Rules
 
+> Full coding standards with examples: see AGENTS.md
+
 ## Project
 
 React hooks/components library. Monorepo: `packages/core` + `packages/mobile`.
 
 ## Architecture
 
 Unidirectional layers: `components → hooks → utils → _internal`
-Mobile depends on core. Core must NOT depend on mobile.
+Core and mobile are independent packages. No cross-package dependencies.
 
 ## Code Style
 
@@ -16,62 +18,10 @@ Mobile depends on core. Core must NOT depend on mobile.
 - Named exports only, no default exports
 - No `any` — strict TypeScript
 - `.ts`/`.tsx` extensions in source imports (tsup converts to `.js`)
-- Strict boolean checks: `value !== undefined` not `if (value)`
+- No implicit boolean coercion: `if (value)` → `if (value != null)` (enforced by `strict-boolean-expressions`)
+- Nullish checks: `== null` for both null and undefined, `!== undefined` only when distinction matters
 - Zero runtime dependencies
 - Always return cleanup in useEffect to remove listeners
-- Nullish checks: `== null` for both null and undefined, `!== undefined` only when distinction matters
 - Early returns (guard clauses) over nested if-else blocks
 - Function declarations use `function` keyword, not arrow: `function toggle(state: boolean) { return !state; }`
 - Short inline callbacks (map, filter args) are OK with arrow functions
-
-## SSR-Safe Pattern
-
-```ts
-const [state, setState] = useState(FIXED_INITIAL_VALUE);
-useEffect(function syncBrowserState() {
-  if (isServer()) return;
-  setState(getBrowserAPI());
-}, []);
-```
-
-## Hook Returns
-
-- 1 value → direct return
-- 2 values → tuple `[state, action]`
-- 3+ values → object `{ a, b, c }`
-
-## Testing
-
-- 100% coverage (Vitest)
-- SSR tests required for browser API hooks (`.ssr.test.ts`)
-- Use `renderHookSSR.serverOnly()` for SSR tests
-
-## File Structure
-
-Each hook in own folder: `src/hooks/useHookName/`
-
-- `index.ts`, `useHookName.ts`, `useHookName.spec.ts` (core) / `.test.ts` (mobile), `useHookName.ssr.test.ts`
-- Docs: `useHookName.md` + `ko/useHookName.md`
-
-## JSDoc
-
-Required tags: `@description`, `@param`, `@returns`, `@example`
-
-## Performance
-
-- Throttle subscriptions at ~16ms (60fps)
-- Use `startTransition` for non-urgent state updates
-
-## Commands
-
-```bash
-yarn build      # Build all (tsup)
-yarn test       # Run tests (Vitest)
-yarn fix        # Auto-fix lint + format
-yarn typecheck  # Type check (tsc --noEmit)
-```
-
-## Commits
-
-Format: `<type>(<scope>): <description>`
-Types: feat, fix, docs, chore, refactor, test

.github/copilot-instructions.md

@@ -1,10 +1,12 @@
 # Copilot Instructions for react-simplikit
 
+> Full coding standards with examples: see [AGENTS.md](../../AGENTS.md)
+
 ## Quick Reference
 
 - Monorepo: `packages/core` (react-simplikit) + `packages/mobile` (@react-simplikit/mobile)
 - Architecture: `components → hooks → utils → _internal` (unidirectional, no circular imports)
-- Mobile depends on core; core must NOT depend on mobile
+- Core and mobile are independent packages — no cross-package dependencies
 
 ## Code Style Rules
 
@@ -13,88 +15,10 @@
 - No default exports — named exports only
 - No `any` types — strict TypeScript
 - Use `.ts`/`.tsx` extensions in source imports (tsup converts to `.js`)
-- Strict boolean checks: `value !== undefined` not `if (value)`
+- No implicit boolean coercion: `if (value)` → `if (value != null)` (enforced by `strict-boolean-expressions`)
+- Nullish checks: `== null` for both null and undefined, `!== undefined` only when distinction matters
 - Zero runtime dependencies
 - Always return cleanup in useEffect to remove listeners
-- Nullish checks: use `== null` for both null and undefined:
-  ```ts
-  if (ref == null) { continue; }
-  items.filter(item => item != null);
-  const controlled = valueProp !== undefined; // only when distinction matters
-  ```
 - Prefer early returns (guard clauses) over nested if-else blocks
-- Function declarations use `function` keyword, not arrow functions:
-  ```ts
-  // ✅ function toggle(state: boolean) { return !state; }
-  // ✅ items.filter(item => item != null)  ← inline callback arrow OK
-  // ❌ const toggle = (state: boolean) => !state;
-  ```
-
-## SSR-Safe Pattern (CRITICAL)
-
-All browser API access must use this pattern:
-
-```ts
-const [state, setState] = useState(FIXED_INITIAL_VALUE);
-useEffect(function syncBrowserState() {
-  if (isServer()) return;
-  setState(getBrowserAPI());
-}, []);
-```
-
-Never call browser APIs during state initialization.
-
-## Hook Return Values
-
-- 1 value → return directly: `useDebounce<T>(value, delay): T`
-- 2 values → tuple: `useToggle(init): [boolean, () => void]`
-- 3+ values → object: `usePagination(): { page, nextPage, prevPage }`
-
-## Testing
-
-- 100% coverage required (Vitest)
-- SSR test required for browser API hooks:
-  ```ts
-  import { renderHookSSR } from '../../_internal/test-utils/renderHookSSR.tsx';
-  it('is safe on server side rendering', () => {
-    const result = renderHookSSR.serverOnly(() => useHookName());
-    expect(result.current).toBeDefined();
-  });
-  ```
-
-## JSDoc Template
-
-Every public API requires:
-
-````ts
-/**
- * @description Brief description of what it does
- * @param paramName - Parameter description
- * @returns What the hook/function returns
- * @example
- * ```ts
- * const value = useHookName(param);
- * ```
- */
-````
-
-## File Structure
-
-```
-src/hooks/useHookName/
-├── index.ts               # Re-export
-├── useHookName.ts         # Implementation
-├── useHookName.spec.ts    # Tests (core) / useHookName.test.ts (mobile)
-├── useHookName.ssr.test.ts # SSR tests
-├── useHookName.md         # English docs
-└── ko/useHookName.md      # Korean docs
-```
-
-## Commands
-
-```bash
-yarn build      # Build all packages (tsup)
-yarn test       # Run tests (Vitest)
-yarn fix        # Auto-fix lint + format
-yarn typecheck  # Type check (tsc --noEmit)
-```
+- Function declarations use `function` keyword, not arrow functions
+- Short inline callbacks (map, filter args) are OK with arrow functions

AGENTS.md

@@ -21,7 +21,7 @@ components → hooks → utils → _internal
 - Components may use hooks, utils, \_internal
 - Hooks may use utils, \_internal
 - Utils may use \_internal only
-- Mobile may depend on core; core must NOT depend on mobile
+- Core and mobile are independent packages — no cross-package dependencies
 
 ## File Structure
 
@@ -42,7 +42,7 @@ src/hooks/useHookName/
 
 - **`type` over `interface`** — Always use `type` for type aliases
 - **Named functions in useEffect** — `useEffect(function handleResize() { ... }, [])` not arrow functions
-- **Strict boolean checks** — `value !== undefined` not `if (value)`
+- **No implicit boolean coercion** — `if (value)` → `if (value != null)` (enforced by `strict-boolean-expressions`)
 - **Import extensions** — Use `.ts`/`.tsx` extensions in source imports (tsup converts to `.js` for ESM output)
 - **Named exports only** — No default exports
 - **No `any` types** — Full TypeScript strict mode