feat: multi-tab instrument analysis

Each /instruments/:id navigation opens a persistent tab in the TabBar.
Multiple instruments can be open simultaneously — state is preserved when switching.

- TabsContext: adds instrumentIds[], openInstrument(), closeInstrument()
- TabBar: renders instrument tabs (teal, monospaced, TrendingUp icon) after static tabs, separated by a divider
- InstrumentDashboard: accepts instrumentIdProp so keep-alive instances use the right id regardless of URL
- App: InstrumentRoute registers the tab on navigation; InstrumentKeepAlive mounts one dashboard per open instrument; NormalRoutes hides on instrument paths (hidden div, Routes still fires)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/src/context/TabsContext.tsx

@@ -1,19 +1,26 @@
 import { createContext, useContext, useCallback, useState, ReactNode } from 'react'
 
 interface TabsCtx {
-  kept:        ReadonlySet<string>
-  keepRoute:   (r: string) => void
-  forgetRoute: (r: string) => void
+  kept:            ReadonlySet<string>
+  keepRoute:       (r: string) => void
+  forgetRoute:     (r: string) => void
+  instrumentIds:   string[]
+  openInstrument:  (id: string) => void
+  closeInstrument: (id: string) => void
 }
 
 const Ctx = createContext<TabsCtx>({
   kept: new Set(),
-  keepRoute:   () => {},
-  forgetRoute: () => {},
+  keepRoute:       () => {},
+  forgetRoute:     () => {},
+  instrumentIds:   [],
+  openInstrument:  () => {},
+  closeInstrument: () => {},
 })
 
 export function TabsProvider({ children }: { children: ReactNode }) {
   const [kept, setKept] = useState<Set<string>>(new Set())
+  const [instrumentIds, setInstrumentIds] = useState<string[]>([])
 
   const keepRoute = useCallback((r: string) =>
     setKept(p => p.has(r) ? p : new Set([...p, r])), [])
@@ -21,7 +28,17 @@ export function TabsProvider({ children }: { children: ReactNode }) {
   const forgetRoute = useCallback((r: string) =>
     setKept(p => { const n = new Set(p); n.delete(r); return n }), [])
 
-  return <Ctx.Provider value={{ kept, keepRoute, forgetRoute }}>{children}</Ctx.Provider>
+  const openInstrument = useCallback((id: string) =>
+    setInstrumentIds(p => p.includes(id) ? p : [...p, id]), [])
+
+  const closeInstrument = useCallback((id: string) =>
+    setInstrumentIds(p => p.filter(x => x !== id)), [])
+
+  return (
+    <Ctx.Provider value={{ kept, keepRoute, forgetRoute, instrumentIds, openInstrument, closeInstrument }}>
+      {children}
+    </Ctx.Provider>
+  )
 }
 
 export const useTabs = () => useContext(Ctx)