feat(site): Palette/Periodic toggle in Language, rename Why → The Case

Two homepage tweaks:

- Section 02 (The Language) gets a pill-style Palette / Periodic view
  toggle at the top-right of the intro row. Palette (fisheye command
  gallery) is default; Periodic (the periodic table) is behind a tab
  click. Collapses the section's vertical footprint substantially
  without losing the signature periodic-table visualization.
- Section 04 renamed "Why Impeccable" → "The Case". Matches the
  editorial voice of "The Language" / "The Antidote" / "The Editors"
  (changelog signature). Sticky nav label Case.

public/css/workflow.css

@@ -3191,3 +3191,66 @@
   }
   .live-demo-caption::before { animation: none; }
 }
+
+/* ============================================
+   LANGUAGE section — Palette / Periodic tabs
+   ============================================ */
+
+.language-intro-row {
+  display: flex;
+  align-items: flex-end;
+  justify-content: space-between;
+  gap: var(--spacing-lg);
+  margin-bottom: var(--spacing-xl);
+}
+
+.language-intro-row .section-lead {
+  margin: 0;
+  flex: 1;
+}
+
+.language-view-toggle {
+  display: inline-flex;
+  gap: 2px;
+  padding: 3px;
+  background: var(--color-mist);
+  border-radius: 999px;
+  flex-shrink: 0;
+}
+
+.language-view-tab {
+  font-family: var(--font-mono);
+  font-size: 0.6875rem;
+  letter-spacing: 0.14em;
+  text-transform: uppercase;
+  padding: 8px 18px;
+  background: transparent;
+  border: 0;
+  border-radius: 999px;
+  color: var(--color-ash);
+  cursor: pointer;
+  transition: background 200ms var(--ease-out), color 200ms var(--ease-out);
+}
+
+.language-view-tab:hover { color: var(--color-ink); }
+
+.language-view-tab.is-active {
+  background: var(--color-paper);
+  color: var(--color-ink);
+  box-shadow: 0 1px 3px oklch(0% 0 0 / 0.08);
+}
+
+.language-view-tab:focus-visible {
+  outline: 2px solid var(--color-accent);
+  outline-offset: 2px;
+}
+
+.language-view { display: none; }
+.language-view.is-active { display: block; }
+
+@media (max-width: 680px) {
+  .language-intro-row {
+    flex-direction: column;
+    align-items: flex-start;
+  }
+}