feat(app): keep prompt state in tabs (#33566)

packages/app/src/context/tab-memory.ts

@@ -0,0 +1,33 @@
+import { createRoot, type Owner } from "solid-js"
+
+type Entry = {
+  value: unknown
+  dispose: VoidFunction
+}
+
+export function createTabMemory(owner: Owner | null) {
+  const entries = new Map<string, Map<string, Entry>>()
+
+  const remove = (key: string) => {
+    const state = entries.get(key)
+    if (!state) return
+    for (const entry of state.values()) entry.dispose()
+    entries.delete(key)
+  }
+
+  return {
+    ensure<T>(key: string, name: string, init: () => T) {
+      const state = entries.get(key) ?? new Map<string, Entry>()
+      if (!entries.has(key)) entries.set(key, state)
+      const existing = state.get(name)
+      if (existing) return existing.value as T
+      const entry = createRoot((dispose) => ({ value: init(), dispose }), owner)
+      state.set(name, entry)
+      return entry.value
+    },
+    remove,
+    dispose() {
+      for (const key of entries.keys()) remove(key)
+    },
+  }
+}