feat(marketing): trim landing to hero, crew, hierarchy, security

Remove the Pitch, One-click, Works, Always-on and Skills sections and the
"Build your AI crew" footer CTA banner. Page is now Hero → CrewStrip →
Hierarchy → Security → FAQ → footer (dark tier kept). Prune the now-dead
section functions, consts, and imports (Image, skills icons). Repoint the
"marketing rendered" heading assertion (p0/p7/visual) from the removed
Pitch heading to the hero h1 (/agentic systems/); refresh the @visual baseline.

Co-Authored-By: Claude Opus 4.8 <[email protected]>

frontend/tests/e2e/p7-marketing.spec.ts

@@ -12,7 +12,7 @@ test("the marketing landing renders for logged-out visitors @marketing", async (
   await page.goto("/");
   // Hero + nav + our wordmark.
   await expect(
-    page.getByRole("heading", { name: /AI coworkers/ }),
+    page.getByRole("heading", { name: /agentic systems/i }),
   ).toBeVisible();
   await expect(
     page.getByRole("link", { name: "Book a demo" }).first(),