fix(api): render children listing on API section index pages

Update Hugo templates to correctly display API children listing on
section index pages (/influxdb3/core/api/, /influxdb3/enterprise/api/)
instead of the RapiDoc renderer.

- Create layouts/api/section.html for API section pages
- Update layouts/_default/api.html to detect section pages and render
  content directly instead of using RapiDoc
- Clean up layouts/api/list.html debug comment

The issue was that layouts/_default/api.html took precedence over
layouts/api/list.html for section pages due to Hugo's type-based
template lookup. The fix adds .IsSection check to delegate section
pages to appropriate rendering logic.

layouts/_default/api.html

@@ -1,13 +1,61 @@
 {{/*
   API Documentation Default Layout
 
-  Full page layout for API documentation using the renderer abstraction.
-  The renderer (Scalar or RapiDoc) is selected via site.Params.apiRenderer.
+  Fallback layout for API documentation pages.
+  Delegates to appropriate templates based on page type:
+  - Section pages: Use section.html logic (children listing)
+  - Pages with staticFilePath: Use RapiDoc renderer
 
-  Required frontmatter:
-  - staticFilePath: Path to the OpenAPI specification file
+  Note: This template exists as a catch-all but specific templates
+  (api/section.html, api/list.html, api/single.html) should be preferred.
 */}}
 
+{{/* Section pages should render content directly, not use RapiDoc */}}
+{{ if .IsSection }}
+
+{{ partial "header.html" . }}
+{{ partial "topnav.html" . }}
+
+<div class="page-wrapper">
+  {{ partial "sidebar.html" . }}
+
+  <div class="content-wrapper api-content">
+    <div class="api-main">
+      <article class="article article--content api-reference" role="main">
+        <header class="article--header">
+          <h1 class="article--title">{{ .Title }}</h1>
+          {{ with .Description }}
+          <p class="article--description">{{ . }}</p>
+          {{ end }}
+        </header>
+
+        {{/* SECTION INDEX - Show page content (intro + children listing) */}}
+        {{ with .Content }}
+        <section class="api-section-content">
+          {{ . }}
+        </section>
+        {{ else }}
+        {{/* Fallback to partial if no content */}}
+        {{ partial "api/section-children.html" . }}
+        {{ end }}
+
+        {{ partial "article/related.html" . }}
+
+      </article>
+    </div>
+
+    <aside class="api-toc" data-component="api-toc">
+      <h4 class="api-toc-header">ON THIS PAGE</h4>
+      <nav class="api-toc-nav"></nav>
+    </aside>
+  </div>
+</div>
+
+{{ partial "footer.html" . }}
+
+{{ else }}
+{{/* Non-section pages with staticFilePath use RapiDoc renderer */}}
+
 {{ partial "header.html" . }}
 {{ partial "topnav.html" . }}
 
@@ -31,3 +79,5 @@
 </div>
 
 {{ partial "footer.html" . }}
+
+{{ end }}

layouts/api/list.html

@@ -28,8 +28,15 @@
         {{ $hasTag := isset .Params "tag" }}
 
         {{ if not $hasTag }}
-        {{/* SECTION INDEX - Show tag pages from article data */}}
+        {{/* SECTION INDEX - Show page content (intro + children listing) */}}
+        {{ with .Content }}
+        <section class="api-section-content">
+          {{ . }}
+        </section>
+        {{ else }}
+        {{/* Fallback to partial if no content */}}
         {{ partial "api/section-children.html" . }}
+        {{ end }}
 
         {{ else }}
         {{/* TAG PAGE - Show operations or conceptual content */}}

layouts/api/section.html

@@ -0,0 +1,48 @@
+{{/*
+  API Documentation Section Layout
+
+  Used for API section index pages (e.g., /influxdb3/core/api/).
+  Shows page content with children listing instead of RapiDoc renderer.
+
+  For tag pages (with 'tag' param), Hugo uses list.html instead.
+*/}}
+
+{{ partial "header.html" . }}
+{{ partial "topnav.html" . }}
+
+<div class="page-wrapper">
+  {{ partial "sidebar.html" . }}
+
+  <div class="content-wrapper api-content">
+    <div class="api-main">
+      <article class="article article--content api-reference" role="main">
+        <header class="article--header">
+          <h1 class="article--title">{{ .Title }}</h1>
+          {{ with .Description }}
+          <p class="article--description">{{ . }}</p>
+          {{ end }}
+        </header>
+
+        {{/* SECTION INDEX - Show page content (intro + children listing) */}}
+        {{ with .Content }}
+        <section class="api-section-content">
+          {{ . }}
+        </section>
+        {{ else }}
+        {{/* Fallback to partial if no content */}}
+        {{ partial "api/section-children.html" . }}
+        {{ end }}
+
+        {{ partial "article/related.html" . }}
+
+      </article>
+    </div>
+
+    <aside class="api-toc" data-component="api-toc">
+      <h4 class="api-toc-header">ON THIS PAGE</h4>
+      <nav class="api-toc-nav"></nav>
+    </aside>
+  </div>
+</div>
+
+{{ partial "footer.html" . }}