feat(onboarding): add dummy header and sidebar shell for v2

Add static JSX header bar and collapsed sidebar to OnboardingV2 that
visually match the branch's minimal onboarding look without modifying
any shared layout components. Header shows logo + login/signup buttons,
sidebar shows greyed-out nav icons (pointer-events-none).

Also adds SearchProvider wrapper around the feed preview to fix
MainFeedLayout runtime error.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: capJavert

packages/webapp/components/onboarding/OnboardingV2.tsx

@@ -31,6 +31,10 @@ import { ChromeIcon } from '@dailydotdev/shared/src/components/icons/Browser/Chr
 import { MagicIcon } from '@dailydotdev/shared/src/components/icons/Magic';
 import { NewTabIcon } from '@dailydotdev/shared/src/components/icons/NewTab';
 import { TerminalIcon } from '@dailydotdev/shared/src/components/icons/Terminal';
+import { HomeIcon } from '@dailydotdev/shared/src/components/icons/Home';
+import { HotIcon } from '@dailydotdev/shared/src/components/icons/Hot';
+import { EyeIcon } from '@dailydotdev/shared/src/components/icons/Eye';
+import { SquadIcon } from '@dailydotdev/shared/src/components/icons/Squad';
 import { VIcon } from '@dailydotdev/shared/src/components/icons/V';
 import { StarIcon } from '@dailydotdev/shared/src/components/icons/Star';
 import { cloudinaryOnboardingExtension } from '@dailydotdev/shared/src/lib/image';
@@ -1128,7 +1132,65 @@ export const OnboardingV2 = (): ReactElement => {
   }, [githubImportBodyPhase]);
 
   return (
-    <div ref={pageRef} className="onb-page relative" role="presentation">
+    <div
+      ref={pageRef}
+      className="onb-page relative tablet:pt-16 laptop:pl-11"
+      role="presentation"
+    >
+      {/* ── Dummy Header (desktop/tablet only) ── */}
+      <header className="fixed left-0 top-0 z-3 hidden h-16 w-full items-center border-b border-border-subtlest-tertiary bg-background-default px-4 tablet:flex">
+        <Logo
+          position={LogoPosition.Relative}
+          className="!left-0 !top-0 !mt-0 !translate-x-0"
+        />
+        <div className="ml-auto flex items-center gap-3">
+          <button
+            type="button"
+            onClick={openLogin}
+            className="rounded-12 px-3 py-1.5 font-bold text-text-secondary transition-colors duration-200 typo-callout hover:bg-surface-hover"
+          >
+            Log in
+          </button>
+          <button
+            type="button"
+            onClick={() => setShowSignupChooser(true)}
+            className="hover:opacity-90 rounded-12 bg-accent-cabbage-default px-5 py-1.5 font-bold text-white transition-opacity duration-200 typo-callout"
+          >
+            Sign up
+          </button>
+        </div>
+      </header>
+
+      {/* ── Dummy Sidebar (laptop only) ── */}
+      <aside className="pointer-events-none fixed left-0 top-16 z-2 hidden h-[calc(100vh-theme(space.16))] w-11 select-none flex-col border-r border-border-subtlest-tertiary bg-background-default laptop:flex">
+        <nav className="flex flex-col items-center gap-0.5 pt-3">
+          <div className="flex h-9 w-full items-center justify-center">
+            <HomeIcon
+              className="h-5 w-5 text-text-disabled"
+              secondary={false}
+            />
+          </div>
+          <div className="flex h-9 w-full items-center justify-center">
+            <SquadIcon
+              className="h-5 w-5 text-text-disabled"
+              secondary={false}
+            />
+          </div>
+          <div className="flex h-9 w-full items-center justify-center">
+            <HotIcon className="h-5 w-5 text-text-disabled" secondary={false} />
+          </div>
+          <div className="flex h-9 w-full items-center justify-center">
+            <EyeIcon className="h-5 w-5 text-text-disabled" secondary={false} />
+          </div>
+          <div className="flex h-9 w-full items-center justify-center">
+            <TerminalIcon
+              className="h-5 w-5 text-text-disabled"
+              secondary={false}
+            />
+          </div>
+        </nav>
+      </aside>
+
       {/* ── Hero ── */}
       <section
         ref={heroRef}