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,

lib/settings.js

@@ -1,4 +1,4 @@
-import { DEFAULT_SETTINGS, OPEN_IN_VALUES } from "./defaults.js";
+import { DEFAULT_SETTINGS, OPEN_IN_VALUES, MAX_MODEL_CHARS } from "./defaults.js";
 
 // Pure. Layers stored values over the defaults, dropping unknown keys and
 // falling back on wrong types or out-of-range values. A fresh or signed-out
@@ -8,7 +8,7 @@ export function mergeSettings(stored) {
   if (stored === null || typeof stored !== "object") {
     return merged;
   }
-  if (typeof stored.model === "string") {
+  if (typeof stored.model === "string" && stored.model.length <= MAX_MODEL_CHARS) {
     merged.model = stored.model;
   }
   if (typeof stored.temporaryChat === "boolean") {