docs: correct hero claim — "no plaintext at rest", not "no trace on disk"

gopass writes GPG-encrypted blobs to disk and the backup gate writes sealed
.age bundles; only *decrypted* secrets are RAM-only. Fix the tagline, ASCII
box, banner alt-text, and banner.svg prose to state the defensible claim.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/assets/banner.svg

@@ -1,4 +1,4 @@
-<svg width="1200" height="360" viewBox="0 0 1200 360" fill="none" xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Incredigo — guards your credentials in locked memory, leaves no trace on disk">
+<svg width="1200" height="360" viewBox="0 0 1200 360" fill="none" xmlns="http://www.w3.org/2000/svg" role="img" aria-label="Incredigo — no plaintext at rest: decrypted secrets in locked memory, GPG-encrypted on disk">
   <defs>
     <linearGradient id="bg" x1="0" y1="0" x2="1200" y2="360" gradientUnits="userSpaceOnUse">
       <stop offset="0" stop-color="#161210"/>
@@ -35,9 +35,9 @@
   <text x="360" y="158" font-family="'JetBrains Mono','Fira Code',ui-monospace,monospace"
         font-size="68" font-weight="700" letter-spacing="3" fill="#8C5E2E"><tspan>in</tspan><tspan fill="url(#word)">CRED</tspan><tspan>i</tspan><tspan fill="url(#word)">GO</tspan></text>
   <text x="362" y="206" font-family="'Inter','DejaVu Sans',sans-serif"
-        font-size="25" font-weight="500" fill="#C9BBB0">Guards your credentials in locked memory.</text>
+        font-size="25" font-weight="500" fill="#C9BBB0">Decrypted secrets live only in locked memory.</text>
   <text x="362" y="240" font-family="'Inter','DejaVu Sans',sans-serif"
-        font-size="25" font-weight="500" fill="#C9BBB0">Leaves no trace on disk.</text>
+        font-size="25" font-weight="500" fill="#C9BBB0">No plaintext at rest — GPG-encrypted on disk.</text>
 
   <!-- guarantee chips -->
   <g font-family="'JetBrains Mono',ui-monospace,monospace" font-size="16" font-weight="600">