Point shared assets at the portal root

Generated head and hero markup now reference /img/logo.svg rather than a
path relative to the page, so subdirectory pages resolve the single copy at
the root. Also drops a duplicate favicon that sat outside the marker block.

Author: bdbarnett

index.html

@@ -6,13 +6,12 @@
   <!-- PYDEVICES-HEAD-TAGS: START -->
   <title>PyDevices - PyDevices.github.io</title>
   <meta name="description" content="Cross-platform hardware driver engine, board contract specification, and display stack for MicroPython, CircuitPython, CPython, PyScript, and Android.">
-  <link rel="icon" type="image/svg+xml" href="img/logo.svg">
+  <link rel="icon" type="image/svg+xml" href="/img/logo.svg">
   <!-- PYDEVICES-HEAD-TAGS: END -->
   <meta property="og:title" content="PyDevices">
   <meta property="og:description" content="One display & hardware contract across 5 Python runtimes: MicroPython, CircuitPython, CPython, PyScript, and Android.">
   <meta property="og:type" content="website">
   <meta property="og:url" content="https://pydevices.github.io/">
-  <link rel="icon" type="image/svg+xml" href="img/logo.svg">
   <link rel="preconnect" href="https://fonts.googleapis.com">
   <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin>
   <link rel="stylesheet" href="https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@500;600;700&display=swap">
@@ -26,7 +25,7 @@
   <section class="hero wrap">
     <div class="hero-lead">
       <div class="hero-brand">
-        <div class="logo-badge product-mark" style="background: linear-gradient(135deg, var(--tier-1-amber), #d97706);"><img src="img/logo.svg" alt="PyDevices.github.io" width="112" height="112"></div>
+        <div class="logo-badge product-mark" style="background: linear-gradient(135deg, var(--tier-1-amber), #d97706);"><img src="/img/logo.svg" alt="PyDevices.github.io" width="112" height="112"></div>
         <span class="eyebrow" style="color: var(--tier-1-amber);">PyDevices Portal</span>
       </div>
       <h1>One display & hardware contract. 5 Python runtimes.</h1>