fix: prefer the focused frame, bound model length, drop dead flag

lib/defaults.js

@@ -4,6 +4,13 @@
 
 export const OPEN_IN_VALUES = ["new-tab", "background-tab", "new-window"];
 
+// An unbounded model string can, on its own, exceed MAX_URL_CHARS in
+// lib/build-url.js — fitToBudget() only ever trims `q`, so a long enough
+// model silently pushes the whole URL over budget and drops the query
+// entirely with no signal to the user. 200 is generous for any real model
+// slug while keeping the URL budget meaningful.
+export const MAX_MODEL_CHARS = 200;
+
 export const DEFAULT_SETTINGS = {
   model: "",
   temporaryChat: false,