Add client-side search with / shortcut

Lazy-loads /index.json on first keystroke, fuzzy-matches titles and
descriptions, keyboard-navigable results (arrows, Enter, Esc).
Based on https://gist.github.com/cmod/5410eae147e4318164258742dd053993

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

themes/hugo-theme-ipng/assets/styles.scss

@@ -266,7 +266,7 @@ nav {
     justify-content: flex-end;
     flex-flow: row wrap;
     overflow: hidden;
-    margin: auto 2% .6em auto;
+    margin: 0 2% 0 auto;
     padding-left: 2em;
 }
 
@@ -342,6 +342,7 @@ nav li:hover {
     text-align: center;
     display: flex;
     flex-flow: row wrap;
+    align-items: center;
 
     /* $mq-mini or smaller: */ margin: 0; width: 100%; font-size: $base-font-size * 0.8;
     @media #{$mq-small} { margin: 0 5%; width: 90%; font-size: $base-font-size * 0.9; }
@@ -779,3 +780,96 @@ table {
   td {
   }
 }
+
+// Search — sits in the header, replaces nav when active
+#fastSearch {
+  display: none;          // toggled to flex by JS
+  flex: 1;
+  align-items: center;
+  align-self: center;     // vertically align with the header text
+  position: relative;     // anchor for the results dropdown
+  margin: 0;
+
+  input#searchInput {
+    flex: 1;
+    width: 100%;
+    padding: .25em .63em;
+    font-size: 1.1em;     // matches nav a font-size
+    color: $text-dark;
+    background-color: transparent;
+    border: none;         // header border-bottom already provides the bottom line
+    outline: none;
+    box-sizing: border-box;
+
+    &::placeholder { color: $text-very-light; font-style: italic; }
+  }
+
+  ul#searchResults {
+    position: absolute;
+    top: 100%;
+    right: 0;
+    left: 0;
+    list-style: none;
+    margin: 0;
+    padding: 0;
+    background-color: #f7f7f7;  // matches header bg
+    border: 1px solid $tab-border-color;
+    border-top: 2px solid $ipng-orange;
+    box-shadow: 0 4px 12px rgba(0,0,0,0.15);
+    z-index: 200;
+
+    &:empty { display: none; }
+
+    li {
+      border-bottom: 1px solid $tab-border-color;
+
+      &:last-child { border-bottom: none; }
+
+      &.search-message {
+        padding: .5em .63em;
+        color: $text-normal;
+        font-style: italic;
+        font-size: .9em;
+      }
+
+      a {
+        display: block;
+        padding: .4em .63em;
+        text-decoration: none;
+        color: $text-dark;
+
+        &:hover, &:focus {
+          outline: none;
+          background-color: $ipng-orange;
+          color: #fff;
+
+          .meta, .desc { color: rgba(255,255,255,0.85); }
+        }
+
+        .title {
+          display: block;
+          font-size: 1em;
+          font-weight: bold;
+        }
+
+        .meta {
+          display: block;
+          font-size: .72em;
+          color: $text-normal;
+          text-transform: uppercase;
+          letter-spacing: .04em;
+          margin: .1em 0;
+        }
+
+        .desc {
+          display: block;
+          font-size: .85em;
+          color: $text-normal;
+          white-space: nowrap;
+          overflow: hidden;
+          text-overflow: ellipsis;
+        }
+      }
+    }
+  }
+}