fix(alpine): resolve console errors on editor and agent panel

Initialize coverOpen/coverLoading in editorState, render import file info with x-if instead of x-show (null deref), split x-if/x-for on the agent mention menu, guard m.steps.length and use unique keys for the icon picker. Also reduce htmx swap responses to .main-wrapper so shell scripts (agent panel, base inline) are not re-executed on partial navigation.

app/templates/agent_panel.html

@@ -293,7 +293,7 @@
               <div class="fd-steps" x-show="m.steps && m.steps.length" x-cloak>
                 <button class="fd-steps-head" type="button" @click="toggleSteps(m)">
                   <span class="fd-steps-chev" :class="{down: m.stepsOpen}">▶</span>
-                  <span class="fd-steps-count" x-text="m.steps.length === 1 ? '1 étape' : m.steps.length + ' étapes'"></span>
+                  <span class="fd-steps-count" x-text="!m.steps ? '' : (m.steps.length === 1 ? '1 étape' : m.steps.length + ' étapes')"></span>
                   <span class="fd-steps-elem" x-text="m.generating ? 'en cours…' : (m.stepsOpen ? 'réduire' : 'voir le déroulé')"></span>
                 </button>
                 <div class="fd-steps-body" x-show="m.stepsOpen" x-cloak>
@@ -373,18 +373,20 @@
         <template x-if="!mentionLoad && !hasMentionItems">
           <div class="fd-mention-empty">Aucun élément. Tapez un nom de document, page ou base.</div>
         </template>
-        <template x-if="!mentionLoad" x-for="it in mentionItems" :key="it.token || it.key">
-          <div>
-            <div class="fd-mention-sep" x-show="it._sep" x-text="it._sep"></div>
-            <div class="fd-mention-item" x-show="!it._sep" :class="{focus: it._i===mentionFocus}"
-                 @click="pickMention(it)" @mouseenter="setMentionFocus(it._i)">
-              <span class="fd-mention-ico" x-text="it.icon"></span>
-              <div class="fd-mention-main">
-                <div class="fd-mention-lbl" x-text="it.label"></div>
-                <div class="fd-mention-sub" x-text="it.sub"></div>
+        <template x-if="!mentionLoad">
+          <template x-for="it in mentionItems" :key="it.token || it.key">
+            <div>
+              <div class="fd-mention-sep" x-show="it._sep" x-text="it._sep"></div>
+              <div class="fd-mention-item" x-show="!it._sep" :class="{focus: it._i===mentionFocus}"
+                   @click="pickMention(it)" @mouseenter="setMentionFocus(it._i)">
+                <span class="fd-mention-ico" x-text="it.icon"></span>
+                <div class="fd-mention-main">
+                  <div class="fd-mention-lbl" x-text="it.label"></div>
+                  <div class="fd-mention-sub" x-text="it.sub"></div>
+                </div>
               </div>
             </div>
-          </div>
+          </template>
         </template>
       </div>
     </div>