ai: persist agent-history + per-message attribution to localStorage

Reloading the page mid-conversation used to keep the messages (via
LIVE_KEY) but lose the two agent-tracking maps, so:
  - row signatures snapped back to whoever was currently active
  - the next turn after reload didn't include the PRIOR HAND-OFF
    block, even though the transcript clearly had multiple personas

Both maps are now stored alongside the live snapshot:
  AGENTS_KEY        crema.ai.agent-history   set of Agent
  MSG_AGENTS_KEY    crema.ai.message-agents  index -> Agent

Stored as JSON arrays since Maps don't serialize. Hydrated on mount
via useState lazy initializer, persisted on every change via two
useEffects, cleared in lockstep with LIVE_KEY when the operator
hits Clear conversation.

Reload mid-thread now reads identically to the pre-reload state:
- atlas» turns 1-3 stay attributed to atlas
- pythia» turn 4 stays attributed to pythia
- next turn after reload still carries the hand-off note

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app/routes/ai.tsx

@@ -115,6 +115,65 @@ function saveLive(msgs: LLMMessage[]) {
     // Quota exceeded or similar — silently drop persistence.
   }
 }
+/* Per-message agent attribution + the set of agents that have produced
+ * turns in the current conversation. Persisted alongside LIVE_KEY so a
+ * reload mid-thread preserves both who-said-what and the hand-off note
+ * the next turn carries.
+ *
+ * Stored as plain JSON shapes (Maps don't serialize):
+ *   AGENTS_KEY:           Array<[agentId, Agent]>      ← agentHistory
+ *   MSG_AGENTS_KEY:       Array<[index, Agent]>        ← messageAgents
+ */
+const AGENTS_KEY = "crema.ai.agent-history"
+const MSG_AGENTS_KEY = "crema.ai.message-agents"
+
+function loadAgentHistory(): Map<string, Agent> {
+  if (typeof window === "undefined") return new Map()
+  try {
+    const raw = localStorage.getItem(AGENTS_KEY)
+    if (!raw) return new Map()
+    const parsed = JSON.parse(raw)
+    if (Array.isArray(parsed)) return new Map(parsed as [string, Agent][])
+  } catch {}
+  return new Map()
+}
+function saveAgentHistory(m: Map<string, Agent>) {
+  if (typeof window === "undefined") return
+  if (m.size === 0) {
+    localStorage.removeItem(AGENTS_KEY)
+    return
+  }
+  try {
+    localStorage.setItem(AGENTS_KEY, JSON.stringify([...m.entries()]))
+  } catch {}
+}
+
+function loadMessageAgents(): Map<number, Agent> {
+  if (typeof window === "undefined") return new Map()
+  try {
+    const raw = localStorage.getItem(MSG_AGENTS_KEY)
+    if (!raw) return new Map()
+    const parsed = JSON.parse(raw)
+    if (Array.isArray(parsed)) return new Map(parsed as [number, Agent][])
+  } catch {}
+  return new Map()
+}
+function saveMessageAgents(m: Map<number, Agent>) {
+  if (typeof window === "undefined") return
+  if (m.size === 0) {
+    localStorage.removeItem(MSG_AGENTS_KEY)
+    return
+  }
+  try {
+    localStorage.setItem(MSG_AGENTS_KEY, JSON.stringify([...m.entries()]))
+  } catch {}
+}
+function clearAgentMaps() {
+  if (typeof window === "undefined") return
+  localStorage.removeItem(AGENTS_KEY)
+  localStorage.removeItem(MSG_AGENTS_KEY)
+}
+
 function clearLive() {
   if (typeof window === "undefined") return
   localStorage.removeItem(LIVE_KEY)
@@ -369,19 +428,29 @@ function ChatSurface({
   // the new agent knows it's stepping into a transcript started by another
   // persona — without that note it answers as if it produced every prior
   // turn itself, which is jarring.
+  // Both maps are seeded from localStorage so a reload mid-thread keeps
+  // attribution + hand-off context intact. Persisted on every change via
+  // the effect lower down, cleared together with the live snapshot.
   const [agentHistory, setAgentHistory] = useState<Map<string, Agent>>(
-    () => new Map(),
+    () => loadAgentHistory(),
   )
   const prevAgentRef = useRef<Agent | undefined>(activeAgent)
 
   // Per-message agent attribution: which agent produced the assistant
   // message at each index. Populated when a turn finishes streaming, used
-  // in MessageRow to show the right name in the signature line. Survives
-  // until the conversation is cleared.
+  // in MessageRow to show the right name in the signature line.
   const [messageAgents, setMessageAgents] = useState<Map<number, Agent>>(
-    () => new Map(),
+    () => loadMessageAgents(),
   )
 
+  // Persist whenever either map changes.
+  useEffect(() => {
+    saveAgentHistory(agentHistory)
+  }, [agentHistory])
+  useEffect(() => {
+    saveMessageAgents(messageAgents)
+  }, [messageAgents])
+
   // Hand-off prompt — only emitted when this conversation has been touched
   // by more than one agent. Lists prior personas the new agent might see in
   // the transcript.
@@ -439,6 +508,7 @@ function ChatSurface({
   const resetAndClear = useCallback(() => {
     initialLive.current = []
     clearLive()
+    clearAgentMaps()
     setMessages([])
     setAgentHistory(new Map())
     setMessageAgents(new Map())