fix(hanzo): register explore.hanzo.network hosts + real Hanzo brand; testnet chainId 36962; single header per breakpoint

- Add explore.hanzo.network / explore.hanzo.ai (+ test/dev) to the Hanzo
  chainRegistry hostnames so isWhiteLabelMode()==false on those hosts →
  HANZO_BRANDING (real geometric-H logo) resolves and the network/chain
  selectors enable (the dropdown was empty + showed the generic triangle).
- Hanzo testnet chainId 36964 → 36962 (LP-018; was duplicated with devnet).
- TopBar is desktop-only (hidden lg:block); HeaderMobile already block lg:hidden
  → exactly one header per breakpoint (was a double header < lg).

configs/app/chainRegistry.ts

@@ -279,7 +279,7 @@ export const CHAINS: ReadonlyArray<ChainEntry> = [
     vm: 'L2',
     network: 'mainnet',
     chainId: 36963,
-    hostnames: [ 'explore-hanzo.lux.network' ],
+    hostnames: [ 'explore-hanzo.lux.network', 'explore.hanzo.network', 'explore.hanzo.ai' ],
     explorerUrl: 'https://explore-hanzo.lux.network',
     apiUrl: 'https://api-explore-hanzo.lux.network',
     branding: HANZO_BRANDING,
@@ -334,8 +334,8 @@ export const CHAINS: ReadonlyArray<ChainEntry> = [
     label: 'Hanzo AI (Testnet)',
     vm: 'L2',
     network: 'testnet',
-    chainId: 36964,
-    hostnames: [ 'explore-hanzo-test.lux.network' ],
+    chainId: 36962,
+    hostnames: [ 'explore-hanzo-test.lux.network', 'explore-test.hanzo.network' ],
     explorerUrl: 'https://explore-hanzo-test.lux.network',
     apiUrl: 'https://api-explore-hanzo-test.lux.network',
     branding: HANZO_BRANDING,
@@ -391,7 +391,7 @@ export const CHAINS: ReadonlyArray<ChainEntry> = [
     vm: 'L2',
     network: 'devnet',
     chainId: 36964,
-    hostnames: [ 'explore-hanzo-dev.lux.network' ],
+    hostnames: [ 'explore-hanzo-dev.lux.network', 'explore-dev.hanzo.network' ],
     explorerUrl: 'https://explore-hanzo-dev.lux.network',
     apiUrl: 'https://api-explore-hanzo-dev.lux.network',
     branding: HANZO_BRANDING,

ui/snippets/topBar/TopBar.tsx

@@ -63,7 +63,9 @@ const TopBar = () => {
   return (
     <div
       className={ cn(
-        'sticky top-0 left-0 w-full max-w-[100vw] z-sticky',
+        // Desktop-only: HeaderMobile (block lg:hidden) is the sole header below
+        // lg. Without this, both render < lg → a double header (two sign-ins).
+        'hidden lg:block sticky top-0 left-0 w-full max-w-[100vw] z-sticky',
         'border-b border-[var(--color-border-divider)]',
         'backdrop-blur-[16px] bg-[rgba(255,255,255,0.97)] dark:bg-[rgba(16,17,18,0.97)]',
       ) }