hermes.x: new mark everywhere, drop redundant Overview nav link

The new tight mark (filled Hermes figure, acid blue, 64×64 viewBox)
replaces both mark.svg and favicon.svg so every existing reference —
brand nav, hero, branding grid, OG image, favicon — picks it up with
no attribute changes. The old file sat behind weird width="5" / "3"
height="22" attributes that crushed it into a sliver; squared the
dimensions per slot so the mark actually renders.

Also drop the "Overview" link from each page's top nav — Hermes.X in
the brand slot already goes to the index, so Overview sent you to the
same place with a different word. Three pages touched: index,
branding, messenger.

branding/index.html

@@ -44,10 +44,9 @@
 
 <nav class="topnav">
   <a class="brand" href="../">
-    <img src="../assets/mark.svg" alt="Hermes" width="5" height="22" style="display:block">
+    <img src="../assets/mark.svg" alt="Hermes" width="22" height="22" style="display:block">
     <span>Hermes<span class="x">.X</span></span>
   </a>
-  <a href="../">Overview</a>
   <a href="../messenger/">Messenger</a>
   <a href="./" class="here">Branding</a>
   <a href="https://theseus.x/" class="get">Get Theseus</a>
@@ -55,7 +54,7 @@
 
 <header class="hero">
   <div class="mark mark-xl" aria-hidden="true">
-    <img src="../assets/mark.svg" alt="Hermes" width="3" height="22" style="display:block">
+    <img src="../assets/mark.svg" alt="Hermes" width="160" height="160" style="display:block">
   </div>
   <h1>Brand kit</h1>
   <p class="tag">Mark, palette, name, voice. One page so client builds, add-on
@@ -83,19 +82,19 @@
 
   <div class="mark-row">
     <div class="cell">
-      <div class="mark-16"><img src="../assets/mark.svg" alt="Hermes" width="5" height="22" style="display:block"></div>
+      <div class="mark-16"><img src="../assets/mark.svg" alt="Hermes" width="16" height="16" style="display:block"></div>
       <small>16 px — stroke variant (one trail)</small>
     </div>
     <div class="cell">
-      <div class="mark-32"><img src="../assets/mark.svg" alt="Hermes" width="3" height="22" style="display:block"></div>
+      <div class="mark-32"><img src="../assets/mark.svg" alt="Hermes" width="32" height="32" style="display:block"></div>
       <small>32 px — standard (3 tapered trails)</small>
     </div>
     <div class="cell">
-      <div class="mark-64"><img src="../assets/mark.svg" alt="Hermes" width="3" height="22" style="display:block"></div>
+      <div class="mark-64"><img src="../assets/mark.svg" alt="Hermes" width="64" height="64" style="display:block"></div>
       <small>64 px — in-panel</small>
     </div>
     <div class="cell">
-      <div class="mark-neg"><img src="../assets/mark.svg" alt="Hermes" width="3" height="22" style="display:block"></div>
+      <div class="mark-neg"><img src="../assets/mark.svg" alt="Hermes" width="48" height="48" style="display:block"></div>
       <small>on sky background</small>
     </div>
   </div>

index.html

@@ -22,10 +22,9 @@
 
 <nav class="topnav">
   <a class="brand" href="./">
-    <img src="assets/mark.svg" alt="Hermes" width="5" height="22" style="display:block">
+    <img src="assets/mark.svg" alt="Hermes" width="22" height="22" style="display:block">
     <span>Hermes<span class="x">.X</span></span>
   </a>
-  <a href="./" class="here">Overview</a>
   <a href="messenger/">Messenger</a>
   <a href="branding/">Branding</a>
   <a href="https://theseus.x/" class="get">Get Theseus</a>
@@ -33,7 +32,7 @@
 
 <header class="hero">
   <div class="mark" aria-hidden="true">
-    <img src="assets/mark.svg" alt="Hermes" width="3" height="22" style="display:block">
+    <img src="assets/mark.svg" alt="Hermes" width="120" height="120" style="display:block">
   </div>
   <h1>Message by name<span class="x">.</span></h1>
   <p class="tag">End-to-end encrypted DMs over Nostr, addressed by your

messenger/index.html

@@ -85,10 +85,9 @@
 
 <nav class="topnav">
   <a class="brand" href="../">
-    <img src="../assets/mark.svg" alt="Hermes" width="5" height="22" style="display:block">
+    <img src="../assets/mark.svg" alt="Hermes" width="22" height="22" style="display:block">
     <span>Hermes<span class="x">.X</span></span>
   </a>
-  <a href="../">Overview</a>
   <a href="./" class="here">Messenger</a>
   <a href="../branding/">Branding</a>
   <a href="https://theseus.x/" class="get">Get Theseus</a>