Polish Aliki documentation theme (ruby#1742)

## Problem

The Aliki HTML theme has several small visual inconsistencies that add
up when browsing generated documentation: method cards and source
toggles compete for attention, selected and nested navigation states
create uneven spacing, page titles do not clearly distinguish object
kind from object name, section dividers are visually heavy, the footer
can sit awkwardly against the sidebar at narrower desktop widths, and
the desktop search field is not aligned with the main reading column.

These issues make the default generated docs feel less polished than the
underlying content warrants, especially on method-heavy pages and wide
layouts with both side navigation and the table of contents visible.

## Solution

- Add a DESIGN.md contract for the Aliki theme so spacing, color,
navigation, method-card, search, title, and footer decisions are
documented in one place.
- Refine method cards, source controls, borders, and section dividers so
code-object pages read with clearer hierarchy and less visual noise.
- Clarify generated navigation structure by giving the left sidebar and
right table of contents distinct IDs and matching selector names.
- Improve page-title kind labeling, nested sidebar spacing, and footer
behavior across desktop breakpoints.
- Align the desktop search field and dropdown to the main content rail
while preserving the existing mobile search modal behavior.

## Screenshots

### Before

<img width="1181" height="713" alt="Screenshot 2026-06-24 at 15 55 34"
src="https://github.com/user-attachments/assets/50f5aea8-b32d-4223-91a4-2ff0a6b3d0c7"
/>

---

<img width="785" height="409" alt="Screenshot 2026-06-24 at 15 56 45"
src="https://github.com/user-attachments/assets/db1780a6-5de8-4123-9edc-7394629c05e3"
/>

### After

<img width="1182" height="761" alt="Screenshot 2026-06-24 at 15 56 06"
src="https://github.com/user-attachments/assets/c238fb25-cdfc-489d-b870-8a86b31987a2"
/>

---

<img width="760" height="455" alt="Screenshot 2026-06-24 at 15 56 37"
src="https://github.com/user-attachments/assets/2eccc444-60fb-4bb0-a731-02d28d70c65d"
/>

Author: st0012

lib/rdoc/generator/template/aliki/DESIGN.md

@@ -1,4 +1,4 @@
-<aside class="table-of-contents" role="complementary" aria-label="Table of Contents">
+<aside id="table-of-contents" class="table-of-contents" role="complementary" aria-label="Table of Contents">
   <div class="toc-sticky">
     <h3 class="toc-heading">On This Page</h3>
     <nav class="toc-nav" id="toc-nav" aria-label="Page sections">

lib/rdoc/generator/template/aliki/_aside_toc.rhtml

@@ -1,3 +1,3 @@
-<div id="navigation-toggle" role="button" tabindex="0" aria-label="Toggle sidebar" aria-expanded="true" aria-controls="navigation">
+<div id="sidebar-navigation-toggle" role="button" tabindex="0" aria-label="Toggle sidebar" aria-expanded="false" aria-controls="sidebar-navigation">
   <span aria-hidden="true">&#9776;</span>
 </div>

lib/rdoc/generator/template/aliki/_sidebar_toggle.rhtml

@@ -3,7 +3,7 @@
 <%= render '_header.rhtml' %>
 <%= render '_sidebar_toggle.rhtml' %>
 
-<nav id="navigation" role="navigation" hidden>
+<nav id="sidebar-navigation" role="navigation" hidden>
   <%= render '_sidebar_pages.rhtml' %>
   <%= render '_sidebar_sections.rhtml' %>
   <%= render '_sidebar_ancestors.rhtml' %>
@@ -30,8 +30,9 @@
   <% end %>
 
   <span id="<%= h klass.legacy_aref %>" class="legacy-anchor"></span>
-  <h1 id="<%= h klass.aref %>" class="anchor-link <%= klass.type %>">
-    <%= klass.type %> <%= klass.full_name %>
+  <h1 id="<%= h klass.aref %>" class="anchor-link <%= klass.type %> page-title">
+    <span class="page-title-kind"><%= klass.type %></span>
+    <span class="page-title-name"><%= klass.full_name %></span>
   </h1>
 
   <section class="description">
@@ -127,44 +128,49 @@
     <%- methods.each do |method| %>
       <div id="<%= method.aref %>" class="method-detail anchor-link <%= method.is_alias_for ? "method-alias" : '' %>">
         <div class="method-header">
-          <%- if (call_seq = method.call_seq) %>
-            <%- call_seq.strip.split("\n").each_with_index do |call_seq, i| %>
+          <div class="method-heading-group">
+            <%- if (call_seq = method.call_seq) %>
+              <%- call_seq.strip.split("\n").each_with_index do |call_seq, i| %>
+                <div class="method-heading">
+                  <a href="#<%= method.aref %>" title="Link to this method">
+                    <span class="method-callseq">
+                      <%= h(call_seq.strip.
+                          gsub( /^\w+\./m, '')).
+                          gsub(/(.*)[-=]&gt;/, '\1&rarr;') %>
+                    </span>
+                  </a>
+                </div>
+              <%- end %>
+            <%- elsif method.has_call_seq? %>
               <div class="method-heading">
                 <a href="#<%= method.aref %>" title="Link to this method">
-                  <span class="method-callseq">
-                    <%= h(call_seq.strip.
-                        gsub( /^\w+\./m, '')).
-                        gsub(/(.*)[-=]&gt;/, '\1&rarr;') %>
-                  </span>
+                  <span class="method-name"><%= h method.name %></span>
+                </a>
+              </div>
+            <%- else %>
+              <div class="method-heading">
+                <a href="#<%= method.aref %>" title="Link to this method">
+                  <span class="method-name"><%= h method.name %></span>
+                  <span class="method-args"><%= h method.param_seq %></span>
                 </a>
               </div>
             <%- end %>
-          <%- elsif method.has_call_seq? %>
-            <div class="method-heading">
-              <a href="#<%= method.aref %>" title="Link to this method">
-                <span class="method-name"><%= h method.name %></span>
-              </a>
-            </div>
-          <%- else %>
-            <div class="method-heading">
-              <a href="#<%= method.aref %>" title="Link to this method">
-                <span class="method-name"><%= h method.name %></span>
-                <span class="method-args"><%= h method.param_seq %></span>
-              </a>
-            </div>
-          <%- end %>
 
-          <%- if (sig_html = type_signature_html(method, klass.path)) %>
-          <pre class="method-type-signature"><code><%= sig_html %></code></pre>
+            <%- if (sig_html = type_signature_html(method, klass.path)) %>
+            <pre class="method-type-signature"><code><%= sig_html %></code></pre>
+            <%- end %>
+          </div>
+
+          <%- if method.token_stream %>
+            <div class="method-controls">
+              <details class="method-source-toggle">
+                <summary><span class="method-source-icon" aria-hidden="true">{}</span> Source</summary>
+              </details>
+            </div>
           <%- end %>
         </div>
 
         <%- if method.token_stream %>
-          <div class="method-controls">
-            <details class="method-source-toggle">
-              <summary>Source</summary>
-            </details>
-          </div>
           <div class="method-source-code" id="<%= method.html_name %>-source">
             <pre class="<%= method.source_language %>"><%= method.markup_code %></pre>
           </div>