Add hash routing and Dota 2 logo to relations preview.

- New web/relations/router.js (parseHash/serializeHash/installRouter):
  top tabs, hero + detail sub-tab, item, patch version, tag filters and
  search query all sync to URL (#/heroes/axe/core, ?tags=...&q=...);
  pushState for discrete picks, replaceState for debounced search.
- export_relations_site.py copies router.js so static export deep-links.
- Header shows dota2_logo.png + title, served via /ui-icon/ whitelist.
- fetch_dota2_logo.py fetches the transparent emblem asset.
- Docs: CHANGELOG / README / DESIGN / AGENTS updated.

web/relations/style.css

@@ -42,6 +42,39 @@ body {
   background: rgba(8, 12, 20, 0.45);
   flex: 0 0 auto;
 }
+/* Brand mark: official Dota 2 logo + 上分帝 title, pinned to the top-left
+   corner of the topbar. Absolutely positioned so the centered tab row and
+   toolbar layout are left untouched. */
+.brand {
+  position: absolute;
+  left: 20px;
+  top: 12px;
+  height: 40px;
+  display: flex;
+  align-items: center;
+  gap: 12px;
+  pointer-events: none;
+  z-index: 2;
+}
+.brand-logo {
+  height: 34px;
+  width: auto;
+  display: block;
+}
+.brand-title {
+  font-size: 18px;
+  font-weight: 700;
+  letter-spacing: 0.16em;
+  color: var(--text);
+  white-space: nowrap;
+  text-shadow: 0 1px 2px rgba(0, 0, 0, 0.6);
+}
+@media (max-width: 880px) {
+  .brand-title { display: none; }
+}
+@media (max-width: 620px) {
+  .brand { display: none; }
+}
 .main-tabs {
   display: flex;
   justify-content: center;
@@ -1532,14 +1565,23 @@ body:has(#items-view:not(.hidden)) {
 }
 .patches-title {
   margin: 0;
-  font-size: 26px;
-  font-weight: 700;
-  letter-spacing: 0.02em;
-  color: var(--text);
+  display: flex;
+  flex-direction: column;
+  align-items: flex-start;
+  gap: 4px;
+}
+.patches-kicker {
+  font-size: 15px;
+  font-weight: 600;
+  color: var(--muted);
+  letter-spacing: 0.14em;
 }
 .patches-ver {
-  color: var(--sel);
-  margin-left: 4px;
+  font-size: 40px;
+  font-weight: 800;
+  color: var(--text);
+  letter-spacing: 0.02em;
+  line-height: 1;
 }
 #patch-select {
   flex: 0 1 auto;