feat(screener): useScreenerMode hook (form|canvas + localStorage)

src/pages/stock/screener/hooks/useScreenerMode.js

@@ -0,0 +1,25 @@
+import { useState } from 'react';
+
+const STORAGE_KEY = 'screener-mode-v1';
+const VALID_MODES = new Set(['form', 'canvas']);
+
+function readMode() {
+  try {
+    const v = localStorage.getItem(STORAGE_KEY);
+    return VALID_MODES.has(v) ? v : 'form';
+  } catch {
+    return 'form';
+  }
+}
+
+export function useScreenerMode() {
+  const [mode, setModeState] = useState(readMode);
+
+  const setMode = (m) => {
+    if (!VALID_MODES.has(m)) return;
+    setModeState(m);
+    try { localStorage.setItem(STORAGE_KEY, m); } catch {}
+  };
+
+  return { mode, setMode };
+}