fix: model select showed a value that was never saved

Root cause of "設定値が不正です (モデルが設定されていません)" despite the
settings UI showing a selected model:
- fillModels(models, selected="") never set option.selected when no model
  was saved yet. The browser then auto-selects the first option visually,
  so the UI displayed e.g. "glm-5.3:cloud" while storage.model remained
  empty. Translation therefore failed with the no-model error until the
  user pressed Save, which materialized the UI value into storage.

Fixes
- popup.js/options.js fillModels: when no model is saved and the list is
  non-empty, explicitly select the first model so the UI value always
  matches what will be used
- popup.js: after the model list loads, persist the auto-selected model
  if storage still has none
- options.js loadSettings: same sync after loadModels, so opening the
  options page also heals the empty-model state

Results: 73 passed, 0 failed. dist rebuilt.

1 files changed, 16 insertions, 0 deletions

diff --git a/src/popup/popup.js b/src/popup/popup.js
index 612d0fd..eb213f5 100644
--- a/src/popup/popup.js
+++ b/src/popup/popup.js
@@ -46,6 +46,13 @@ function fillModels(models, selected) {
     option.selected = true;
     $model.append(option);
   }
+  if (!selected && models.length > 0) {
+    // No model saved yet: explicitly select the first one so the UI value
+    // matches what will be used. Otherwise the browser auto-selects the
+    // first option visually while storage still has an empty model,
+    // which made translation fail until the user pressed Save.
+    $model.selectedIndex = 0;
+  }
 }
 
 function showStatus(message, isError) {
@@ -128,4 +135,13 @@ $openOptions.addEventListener('click', () => {
 void (async () => {
   await loadSettings();
   await loadModels();
+  // If the model list loaded and no model is saved yet, persist the
+  // auto-selected first model so the stored settings match the UI.
+  if (knownModels.length > 0) {
+    const result = await browser.storage.local.get({ settings: null });
+    const stored = sanitizeSettings(result.settings || defaultSettings());
+    if (!stored.model) {
+      await persist({ model: $model.value });
+    }
+  }
 })();
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