feat: adopt the rebalanced mark and add a wordmark lockup

The shipped mark failed the one size it most needed to survive. At 16px
in a browser tab its outer strokes rasterised away entirely and the
2.5px gap between stroke and node filled in, so the favicon rendered as
an indeterminate horizontal smear rather than as anything. Three changes
fix it, all driven by that case and verified by rendering rather than by
reasoning: strokes stop at x=30 so the gap survives, outer opacity goes
.45/.55 -> .7 so the neighbours stay visible, and the node grows to
r=8.5 so it still reads as a disc.

This is not a rebrand. The mark is the same three-signals-converging
figure and keeps whatever recognition it has earned; only its
proportions changed. icon.svg and logo.svg had drifted slightly apart
(different node radii and stroke ends) and are now geometrically
identical, differing only in palette.

Adds the lockup, which had no asset at all, in two variants because one
cannot serve both jobs: public/lockup.svg uses currentColor for in-app
use, and docs/assets/lockup.svg fixes the colour to #0092fd for the
README. An <img src> reference resolves currentColor to black, so the
currentColor variant would be invisible against a dark README. The
wordmark carries textLength, without which it overruns the viewBox on
wider monospace fonts.

Concepts and the reasoning behind the ones not chosen are on the
docs/logo-concepts branch.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

apps/web/public/lockup.svg

@@ -0,0 +1,24 @@
+<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 283 64" width="283" height="64" role="img" aria-label="shared-memory">
+  <title>shared-memory</title>
+  <!--
+    Horizontal lockup for headers, docs, and the OAuth consent screen, where a
+    bare 64px glyph is too little and the full app header is too much.
+
+    currentColor, so it inherits the surrounding text colour. That does NOT
+    survive being referenced as <img src>, which resolves currentColor to
+    black - use docs/assets/lockup.svg for anything outside the app.
+
+    `textLength` is not decoration: the wordmark is set in whatever monospace
+    the viewer has, and without a locked advance width the text overruns the
+    viewBox on wider fonts.
+  -->
+  <g fill="none" stroke="currentColor" stroke-linecap="round" stroke-width="7">
+    <path d="M12 16C24 16 25 32 30 32" opacity=".7"/>
+    <path d="M12 32H30"/>
+    <path d="M12 48C24 48 25 32 30 32" opacity=".7"/>
+  </g>
+  <circle cx="46" cy="32" r="8.5" fill="currentColor"/>
+  <text x="72" y="41" fill="currentColor" textLength="203" lengthAdjust="spacingAndGlyphs"
+        font-family="ui-monospace, SFMono-Regular, Menlo, Consolas, monospace"
+        font-size="26" letter-spacing="-0.8">shared<tspan opacity=".45">-</tspan>memory</text>
+</svg>