css: fix positioning of search button in tag search box.

Fixes the search button wrapping to the next line in Firefox. Also fixes
the search box to be full width with no gap between the search box and
the search button.

app/javascript/src/styles/common/main_layout.scss

@@ -32,20 +32,6 @@ div#page {
       list-style-type: none;
     }
 
-    input[type=text] {
-      /* ensure expanded search box renders above post thumbnails. */
-      z-index: 1;
-      position: relative;
-    }
-
-    button[type=submit] {
-      padding: 2px 6px;
-    }
-
-    #search-box button[type=submit] {
-      border-left: none;
-    }
-
     #options-box i.fa-bookmark {
       margin-right: 0.25em;
     }

app/javascript/src/styles/specific/posts.scss

@@ -279,6 +279,16 @@ div#c-posts {
     margin-left: 1em;
   }
 
+  #search-box-form {
+    display: flex;
+
+    #search-box-submit {
+      padding: 2px 6px;
+      border-left: none;
+      border-radius: 0px;
+    }
+  }
+
   div#a-index {
     menu#post-sections {
       margin-bottom: 0.5em;

app/javascript/src/styles/specific/z_responsive.scss

@@ -33,7 +33,7 @@
     padding: 5px;
 
     input#tags {
-      width: 80%;
+      min-width: 0px;
     }
 
     button[type=submit] {

app/views/posts/partials/common/_search.html.erb

@@ -2,14 +2,15 @@
 
 <section id="search-box">
   <h1>Search</h1>
-  <%= form_tag(path, :method => "get") do %>
+  <%= form_tag(path, method: "get", id: "search-box-form") do %>
     <% if params[:raw] %>
       <%= hidden_field_tag :raw, params[:raw] %>
     <% end %>
     <% if params[:random] %>
       <%= hidden_field_tag :random, params[:random] %>
     <% end %>
-    <%= text_field_tag("tags", tags, :id => tags_dom_id, :"data-shortcut" => "q", :"data-autocomplete" => "tag-query") %><%= content_tag "button", content_tag("i", nil, class: "fas fa-search"), type: "submit" %>
+    <%= text_field_tag("tags", tags, :id => tags_dom_id, :"data-shortcut" => "q", :"data-autocomplete" => "tag-query") %>
+    <button id="search-box-submit" type="submit"><i class="fas fa-search"></i></button>
     <%= hidden_field_tag "ms", "1" %>
   <% end %>
 </section>