swarm-ui: brand text follows the nav accent too

The brand/logo text now rides the same accent value the nav underline
uses, including mid-sweep, so the header reads as one accent changing
rather than the underline alone — per mara's review comment.

frontend/packages/swarm-ui/src/shell/Shell.css

@@ -30,8 +30,28 @@
 }
 .shell-brand {
   font-weight: 600;
+  /* Base colour only — Shell.tsx overrides it inline to the same
+     currently-active-tab accent `.shell-nav-indicator` uses (falling
+     back to this `--purple` before the first measurement lands, which
+     is also the "hives" default route's own accent, so there's no
+     visible mismatch at first paint). Transition lives here, same
+     140ms hop cadence + the same three-rule motion guard as the
+     indicator, so this and the indicator read as one thing changing,
+     not two independently-synced ones. */
   color: var(--purple);
   letter-spacing: 0.02em;
+  transition: color 140ms ease;
+}
+@media (prefers-reduced-motion: reduce) {
+  .shell-brand {
+    transition: none;
+  }
+}
+:root[data-motion='reduce'] .shell-brand {
+  transition: none;
+}
+:root[data-motion='allow'] .shell-brand {
+  transition: color 140ms ease;
 }
 .shell-nav {
   display: flex;

frontend/packages/swarm-ui/src/shell/Shell.tsx

@@ -24,6 +24,8 @@
 // through the existing base16 chromatic slots (`NAV_ITEMS`' `accent`
 // field), not a continuous hue rotation — everything here still
 // derives from base16, same rule the rest of the palette follows.
+// `.shell-brand` rides the identical accent value (`navAccent` below),
+// so the header reads as one accent changing, not the underline alone.
 import { useEffect, useRef, useState } from 'preact/hooks';
 import type { ComponentChildren } from 'preact';
 import { Link, useLocation } from 'wouter-preact';
@@ -218,10 +220,18 @@ export function Shell({ children }: { children: ComponentChildren }) {
     document.title = brand;
   }, [brand]);
 
+  // Same value the indicator itself is drawn with, including mid-sweep —
+  // the brand text rides the identical hop sequence rather than
+  // computing its own, so "the header's accent" reads as one thing
+  // changing, not two things that happen to agree at rest.
+  const navAccent = indicator?.accent ?? 'var(--purple)';
+
   return (
     <div class="shell">
       <header class="shell-header">
-        <span class="shell-brand">{brand}</span>
+        <span class="shell-brand" style={{ color: navAccent }}>
+          {brand}
+        </span>
         <nav class="shell-nav" ref={navRef}>
           {NAV_ITEMS.map((item) => (
             <NavLink