refactor: remove search button from FAB, reorganize 7-button layout

Remove cmd-k-btn (search) from floating action buttons - search now only
lives in the action bar. Recalculated positions for 7-button (desktop)
and 6-button (mobile without shortcuts) layouts using fluid clamp() sizing.

static/css/04-interactive/_buttons.css

@@ -124,7 +124,7 @@
     color: #27ae60; /* Green icon when at bottom */
 }
 
-/* Download Button (TOP POSITION) */
+/* Download Button (TOP POSITION - now first button after cmd-k removed) */
 .download-btn {
     position: fixed;
     bottom: 26rem; /* Top button position */
@@ -172,43 +172,6 @@
     background: #cd6060 !important; /* PDF red - matches hover */
 }
 
-/* CMD+K Command Bar Button (TOP position - first button) */
-.cmd-k-btn {
-    position: fixed;
-    bottom: 30rem; /* TOP position - above download button */
-    left: 2rem; /* Left side */
-    width: 50px;
-    height: 50px;
-    background: var(--black-bar, #2b2b2b);
-    color: white;
-    border: none;
-    border-radius: 50%;
-    cursor: pointer;
-    display: flex;
-    align-items: center;
-    justify-content: center;
-    box-shadow: 0 4px 12px rgba(0, 0, 0, 0.3);
-    transition: all 0.3s ease;
-    z-index: 999;
-    opacity: 0.6;
-}
-
-.cmd-k-btn:hover {
-    opacity: 1;
-    transform: translateY(-3px);
-    box-shadow: 0 6px 16px rgba(0, 0, 0, 0.4);
-    background: #00897b; /* Teal - distinct from zoom button purple */
-}
-
-.cmd-k-btn.at-bottom {
-    opacity: 1;
-    background: #00897b; /* Teal - distinct from zoom button purple */
-}
-
-.cmd-k-btn:active {
-    transform: translateY(-1px);
-}
-
 /* Mobile adjustments - now handled by fluid sizing in _scroll-behavior.css
    The 900px media query there uses clamp() for smooth scaling of all buttons and icons */