correct h1 line-height, centralize .cooked styles

app/assets/stylesheets/common/base/topic-post.scss

@@ -20,18 +20,17 @@
  }
 }
 
-.cooked .highlight {
+/* global styles for the cooked HTML content in posts */
+.cooked {
+  word-wrap: break-word;
+  h1, h2, h3, h4, h5, h6 { margin: 30px 0 10px; }
+  h1 { line-height: 1em; } /* normalize.css sets h1 font size but not line height */
+  a { word-wrap: break-word; }
+  .highlight {
     background-color: scale-color($highlight, $lightness: 40%);
     padding: 2px;
     margin: -2px;
-}
-
-.contents .cooked a {
-  word-wrap: break-word;
-}
-
-.contents .cooked {
-  word-wrap: break-word;
+  }
 }
 
 .post-action {

app/assets/stylesheets/desktop/discourse.scss

@@ -148,15 +148,11 @@ body {
 
   h1, h2, h3, h4, h5, h6 {
     margin: 0;
-    font-family: inherit;
-    font-weight: bold;
-    color: inherit;
     text-rendering: optimizelegibility;
   }
 
   .page-not-found {
     margin: 20px 0 40px 0;
-
   }
 
   .page-not-found-search {

app/assets/stylesheets/desktop/topic-post.scss

@@ -602,10 +602,6 @@ iframe {
   position: relative;
 }
 
-.contents .cooked {
-  h1, h2, h3, h4, h5, h6 { margin: 30px 0 10px; }
-}
-
   a.mention {
     padding: 2px 4px;
     color: $primary;

app/assets/stylesheets/mobile/topic-post.scss

@@ -398,10 +398,6 @@ iframe {
   position: relative;
 }
 
-.contents .cooked a {
-  word-wrap: break-word;
-}
-
 .wiki {
   float: left;
   padding: 10px;