feat(frontend): keyboard shortcuts

frontend/src/App.tsx

@@ -18,6 +18,7 @@ import HowItWorks from "./components/HowItWorks"
 import ExampleRepos from "./components/ExampleRepos"
 import { usePrefersReducedMotion } from "./hooks/usePrefersReducedMotion"
 import { useToast } from "./components/Toast"
+import { useKeyboardShortcuts } from "./hooks/useKeyboardShortcuts"
 import { useHistory } from "./hooks/useHistory"
 import HistoryPanel from "./components/HistoryPanel"
 
@@ -93,6 +94,13 @@ export default function App() {
     }
   }
 
+  // Keyboard shortcuts
+  useKeyboardShortcuts({
+    "1": () => setActiveTab("violations"),
+    "2": () => setActiveTab("remediation"),
+    "escape": () => setError(""),
+  })
+
   // Focus management: move focus to results after analysis completes
   useEffect(() => {
     if (result && !loading && resultsRef.current) {

frontend/src/hooks/useKeyboardShortcuts.ts

@@ -0,0 +1,31 @@
+import { useEffect } from "react"
+
+interface Shortcuts {
+  [key: string]: () => void
+}
+
+export function useKeyboardShortcuts(shortcuts: Shortcuts) {
+  useEffect(() => {
+    const handler = (e: KeyboardEvent) => {
+      const target = e.target as HTMLElement
+      if (target.tagName === "INPUT" || target.tagName === "TEXTAREA" || target.isContentEditable) {
+        return
+      }
+
+      const parts: string[] = []
+      if (e.ctrlKey || e.metaKey) parts.push("ctrl")
+      if (e.shiftKey) parts.push("shift")
+      if (e.altKey) parts.push("alt")
+      parts.push(e.key.toLowerCase())
+      const combo = parts.join("+")
+
+      if (combo in shortcuts) {
+        e.preventDefault()
+        shortcuts[combo]()
+      }
+    }
+
+    window.addEventListener("keydown", handler)
+    return () => window.removeEventListener("keydown", handler)
+  }, [shortcuts])
+}