fix(guide): collapsible nav not toggling — reference open/searching directly (Svelte reactivity)

isOpen() helper hid the dependency on `open` from Svelte's tracking, so clicks
updated state but not the view. Inline (searching || open[key]) instead.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/components/GuideReader.svelte

@@ -52,7 +52,6 @@
   $: productApps = filtered.filter(a => a.app !== 'platform' && a.app !== 'technical');
   $: platformApp = filtered.find(a => a.app === 'platform') ?? null;
   $: technicalApp = filtered.find(a => a.app === 'technical') ?? null;
-  const isOpen = (key: string) => searching || !!open[key];
 
   async function loadNav() {
     loadingNav = true;
@@ -110,15 +109,15 @@
         {#if productApps.length}
           <div class="nav-sec">
             <button class="sec-head" on:click={() => toggle('modules')}>
-              <span class="chev">{isOpen('modules') ? '▾' : '▸'}</span> Modules
+              <span class="chev">{(searching || open['modules']) ? '▾' : '▸'}</span> Modules
             </button>
-            {#if isOpen('modules')}
+            {#if (searching || open['modules'])}
               {#each productApps as app (app.app)}
                 <div class="nav-app">
                   <button class="app-head" on:click={() => toggle('app:' + app.app)}>
-                    <span class="chev">{isOpen('app:' + app.app) ? '▾' : '▸'}</span> {appLabel(app.app)}
+                    <span class="chev">{(searching || open['app:' + app.app]) ? '▾' : '▸'}</span> {appLabel(app.app)}
                   </button>
-                  {#if isOpen('app:' + app.app)}
+                  {#if (searching || open['app:' + app.app])}
                     {#each app.modules as m (m.module)}
                       <button class="nav-item nested" class:active={m.module === activeModuleKey}
                         on:click={() => selectModule(m.module)} title={m.module}>{m.title}</button>
@@ -134,9 +133,9 @@
         {#if platformApp}
           <div class="nav-sec">
             <button class="sec-head" on:click={() => toggle('platform')}>
-              <span class="chev">{isOpen('platform') ? '▾' : '▸'}</span> Platform
+              <span class="chev">{(searching || open['platform']) ? '▾' : '▸'}</span> Platform
             </button>
-            {#if isOpen('platform')}
+            {#if (searching || open['platform'])}
               {#each platformApp.modules as m (m.module)}
                 <button class="nav-item" class:active={m.module === activeModuleKey}
                   on:click={() => selectModule(m.module)} title={m.module}>{m.title}</button>
@@ -149,9 +148,9 @@
         {#if technicalApp}
           <div class="nav-sec">
             <button class="sec-head" on:click={() => toggle('technical')}>
-              <span class="chev">{isOpen('technical') ? '▾' : '▸'}</span> Technical
+              <span class="chev">{(searching || open['technical']) ? '▾' : '▸'}</span> Technical
             </button>
-            {#if isOpen('technical')}
+            {#if (searching || open['technical'])}
               {#each technicalApp.modules as m (m.module)}
                 <button class="nav-item" class:active={m.module === activeModuleKey}
                   on:click={() => selectModule(m.module)} title={m.module}>{m.title}</button>