fix(sessions): refresh model from registry on session restore (#502)

Persisted sessions store the full model object including contextWindow.
After a dependency bump that updates registry metadata (e.g. Opus 4.6
going from 200k to 1M context), restored sessions would still show the
old value because setModel() received the stale persisted object.

Now re-resolve the model from getModel(provider, id) on restore, picking
up the latest contextWindow, pricing, and other metadata. Falls back to
the persisted model for custom-gateway models not in the registry.

Author: tmustier

src/taskpane/sessions.ts

@@ -7,6 +7,8 @@
  * - session identity lifecycle (new / rename / resume)
  */
 
+import type { Model } from "@mariozechner/pi-ai";
+import { getModel } from "@mariozechner/pi-ai";
 import type { Agent, AgentMessage } from "@mariozechner/pi-agent-core";
 import type { SessionData } from "@mariozechner/pi-web-ui/dist/storage/types.js";
 import type { SessionsStore } from "@mariozechner/pi-web-ui/dist/storage/stores/sessions-store.js";
@@ -42,6 +44,22 @@ type UserLikeMessage = AgentMessage & {
   content: unknown;
 };
 
+/**
+ * Re-resolve a persisted model against the current registry so that
+ * metadata like `contextWindow` picks up upstream changes (e.g. a dep
+ * bump that raised Opus 4.6 from 200k → 1M). Falls back to the
+ * persisted model if the registry doesn't have it (custom gateways, etc.).
+ */
+// eslint-disable-next-line @typescript-eslint/no-explicit-any -- Model<any> from session store
+function refreshModelFromRegistry(persisted: Model<any>): Model<any> {
+  try {
+    const fresh = getModel(persisted.provider as never, persisted.id as never);
+    return fresh ?? persisted;
+  } catch {
+    return persisted;
+  }
+}
+
 function hasAssistantMessage(messages: AgentMessage[]): boolean {
   return messages.some((m) => m.role === "assistant");
 }
@@ -281,7 +299,7 @@ export async function setupSessionPersistence(opts: {
     agent.replaceMessages(sessionData.messages);
 
     if (sessionData.model) {
-      agent.setModel(sessionData.model);
+      agent.setModel(refreshModelFromRegistry(sessionData.model));
     }
     if (sessionData.thinkingLevel) {
       agent.setThinkingLevel(sessionData.thinkingLevel);