feat: instrument analysis

frontend/src/context/TabsContext.tsx

@@ -1,7 +1,19 @@
-import { createContext, useContext, useCallback, useState, useEffect, ReactNode } from 'react'
+import { createContext, useContext, useCallback, useState, ReactNode } from 'react'
 
-// Instruments that exist in instruments.json — used to validate localStorage
-const VALID_INSTRUMENT_SUFFIX = /^[A-Z0-9]+=?[A-Z0-9-]*$/
+// Forex tickers on Yahoo Finance require the =X suffix; migrate stale plain versions
+const FOREX_MIGRATIONS: Record<string, string> = { 'EURUSD': 'EURUSD=X', 'GBPUSD': 'GBPUSD=X', 'USDJPY': 'USDJPY=X', 'USDCHF': 'USDCHF=X' }
+
+function migrateInstrumentId(id: string): string {
+  return FOREX_MIGRATIONS[id] ?? id
+}
+
+// Apply once at module load so every localStorage read is already corrected
+;(function migrateLastInstrument() {
+  const stored = localStorage.getItem('last_instrument')
+  if (stored && FOREX_MIGRATIONS[stored]) {
+    localStorage.setItem('last_instrument', FOREX_MIGRATIONS[stored])
+  }
+})()
 
 interface TabsCtx {
   kept:            ReadonlySet<string>
@@ -32,8 +44,9 @@ export function TabsProvider({ children }: { children: ReactNode }) {
     setKept(p => { const n = new Set(p); n.delete(r); return n }), [])
 
   const openInstrument = useCallback((id: string) => {
-    localStorage.setItem('last_instrument', id)
-    setInstrumentIds(p => p.includes(id) ? p : [...p, id])
+    const safe = migrateInstrumentId(id.toUpperCase())
+    localStorage.setItem('last_instrument', safe)
+    setInstrumentIds(p => p.includes(safe) ? p : [...p, safe])
   }, [])
 
   const closeInstrument = useCallback((id: string) =>