feat(nav): "All parts" home link on every part page + retint .ok green

Two TOC-navigation fixes after seeing the live site.

1. Part pages had no one-click path back to the index — only the
   numbered Part pills, which all go sideways to other parts.
   Add a leading `.wt-home-link` in the topbar's .part-nav on every
   part page, pointing at the root (`/` locally, `/<basePath>/` on
   GH Pages — the existing applyBasePath rewrite handles it).
   Chevron prefix (`‹ All parts`) distinguishes it from the numbered
   pills; slightly brighter border + right margin reinforce the
   "root vs sibling" grouping.

2. Meander emits the `(N sections)` count on the TOC with class "ok",
   which gets Chakra green from the upstream CSS. Green clashes with
   the Socket lavender surface. Override `.ok` to `var(--muted-lavender)`
   so the count recedes as metadata and the part titles carry the
   visual weight.

Index page has no .part-nav (it IS the index), so the link injection
is a no-op there. The ::before chevron is CSS-only; no inline SVG.

Author: jdalton

scripts/walkthrough.mts

@@ -574,6 +574,21 @@ async function generate(
       html = html.replace('</body>', `  ${footerTag}\n</body>`)
     }
 
+    // Inject a "All parts" home link at the front of the part-nav on
+    // every part page. Meander's emitted topbar only has the numbered
+    // Part pills — users clicking a part had no one-click way back to
+    // the TOC. Index page has no `.part-nav` so the replace is a
+    // no-op there (the TOC IS the index). Idempotent via class marker.
+    if (
+      html.includes('<div class="part-nav">') &&
+      !html.includes('wt-home-link')
+    ) {
+      html = html.replace(
+        '<div class="part-nav">',
+        '<div class="part-nav"><a class="wt-home-link" href="/" aria-label="Back to the walkthrough index">All parts</a>',
+      )
+    }
+
     // Base-path rewrite — last step so every injected tag above gets
     // prefixed in one pass. No-op when --base-path is empty (local dev,
     // Val Town hosting, etc.).

walkthrough-overrides.css

@@ -686,6 +686,28 @@ body.wt-ready .topbar-actions {
   border-color: rgba(255, 255, 255, 0.7) !important;
   font-weight: 600;
 }
+
+/* Meander's default `.ok` class is Chakra-green (#16a34a) for positive
+ * annotations like the "(N sections)" counts on the TOC. Green clashes
+ * with the Socket lavender surface on the index. Retint to muted
+ * lavender so the count recedes as metadata and the part titles carry
+ * the visual weight. */
+.ok {
+  color: var(--muted-lavender) !important;
+}
+/* "All parts" home link on every part page. Leading chevron makes it
+ * unambiguous it's a back-nav, not another Part pill. Slight right
+ * margin + brighter border separate it from the numbered pills so it
+ * reads as a distinct category ("root" vs "children"). */
+.topbar .part-nav a.wt-home-link {
+  border-color: rgba(255, 255, 255, 0.55) !important;
+  margin-right: 8px;
+}
+.topbar .part-nav a.wt-home-link::before {
+  content: '‹ ';
+  margin-right: 2px;
+  opacity: 0.8;
+}
 /* Dark theme keeps the same purple band — docs.socket.dev uses the
  * same header in both modes, deepened slightly against the near-black
  * page. */