refactor(admin): split lib/sdk/context.tsx (1280 LOC) into focused modules

Extract the monolithic SDK context provider into seven focused modules:
- context-types.ts (203 LOC): SDKContextValue interface, initialState, ExtendedSDKAction
- context-reducer.ts (353 LOC): sdkReducer with all action handlers
- context-provider.tsx (495 LOC): SDKProvider component + SDKContext
- context-hooks.ts (17 LOC): useSDK hook
- context-validators.ts (94 LOC): local checkpoint validation logic
- context-projects.ts (67 LOC): project management API helpers
- context-sync-helpers.ts (145 LOC): sync infrastructure init/cleanup/callbacks
- context.tsx (23 LOC): barrel re-export preserving existing import paths

All files under the 500-line hard cap. Build verified with `npx next build`.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

admin-compliance/lib/sdk/context-hooks.ts

@@ -0,0 +1,17 @@
+'use client'
+
+import { useContext } from 'react'
+import { SDKContextValue } from './context-types'
+import { SDKContext } from './context-provider'
+
+// =============================================================================
+// HOOK
+// =============================================================================
+
+export function useSDK(): SDKContextValue {
+  const context = useContext(SDKContext)
+  if (!context) {
+    throw new Error('useSDK must be used within SDKProvider')
+  }
+  return context
+}