fix: consistent tool logo placement across slides

- Use px instead of em so position doesn't shift with font size
- Explicitly set position:relative on sections for reliable anchoring

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

index.html

@@ -32,6 +32,7 @@
     .reveal .slides section {
       text-align: left;
       border-top: 6px solid var(--strip-color);
+      position: relative;
     }
 
     .reveal h1, .reveal h2 {
@@ -63,8 +64,8 @@
 
     .slide-logo {
       position: absolute;
-      bottom: 0.6em;
+      bottom: 12px;
-      right: 0.8em;
+      right: 16px;
       width: 40px;
       height: 40px;
       opacity: 0.8;