Merge: Restore root-level structure + add skills/docs/codebases

- Restored original root-level src/, package.json, etc.
- Added skills/ directory with Claude Code skills
- Added original-docs/ with source documentation
- Added codebases/z-ai-tooling/ as reference codebase
- Updated README.md with complete documentation

Total: Combined 82 original files + new skills structure

codebases/z-ai-tooling/src/hooks/use-mobile.ts

@@ -0,0 +1,19 @@
+import * as React from "react"
+
+const MOBILE_BREAKPOINT = 768
+
+export function useIsMobile() {
+  const [isMobile, setIsMobile] = React.useState<boolean | undefined>(undefined)
+
+  React.useEffect(() => {
+    const mql = window.matchMedia(`(max-width: ${MOBILE_BREAKPOINT - 1}px)`)
+    const onChange = () => {
+      setIsMobile(window.innerWidth < MOBILE_BREAKPOINT)
+    }
+    mql.addEventListener("change", onChange)
+    setIsMobile(window.innerWidth < MOBILE_BREAKPOINT)
+    return () => mql.removeEventListener("change", onChange)
+  }, [])
+
+  return !!isMobile
+}