feat(site): blocos 3D da marca, novas ofertas e hero mais abrangente

Hero e movimento
- cena 3D em tempo real com os blocos da marca (kit feito no Blender, 3d/blocos.py):
  marca, tela, integrações e dados; segue a rolagem, tem vida em repouso, reage ao
  cursor e, parada no topo, passa sozinha pelos estados com legenda
- três níveis de aparelho (full, lite, static); sem WebGL fica o pôster
- título novo: "Sites e sistemas sob medida para o jeito que a sua empresa trabalha."
- faixa de clientes com o ramo, linha do primeiro passo, hero alinhado às seções
- rótulos digitados, entrada dos blocos, cortina de blocos entre páginas e capa
  compartilhada entre a lista de cases e o case

Ofertas
- atendimento no WhatsApp com IA e nota fiscal para a reforma tributária
  (páginas de serviço, cartões da home, formulário e aviso com data de validade)
- página /ia atualizada, com fontes
- peças 3D em loop nos cartões e topos de página (3d/pecas.py)

Design
- hover por papel (bloco nos botões, barra nos links), rótulos sem caixa alta
- um destino por rótulo: "Falar sobre meu projeto" leva ao formulário,
  "Chamar no WhatsApp" abre o WhatsApp
- logo montado em blocos, 404 redesenhado, grades sem célula vazia
- ícones do PWA e manifesto novos

Specs em specs/, contexto de design em DESIGN.md e PRODUCT.md.

lib/device.test.ts

@@ -1,14 +1,16 @@
 import {
   isCoarsePointer,
+  isKnownSlowScene,
   isKnownSoftwareWebGL,
-  isLowPowerDevice,
   isMobileViewport,
   isSaveData,
   isSoftwareRenderer,
   isSoftwareWebGL,
   isWebKit,
   MOBILE_QUERY,
+  rememberSlowScene,
   rememberSoftwareWebGL,
+  sceneTier,
 } from "./device";
 
 const originalMatchMedia = window.matchMedia;
@@ -40,9 +42,11 @@ afterEach(() => {
   window.matchMedia = originalMatchMedia;
 });
 
+const TOUCH = "(pointer: coarse)";
+
 describe("device hints", () => {
   it("treats a capable desktop as full power", () => {
-    expect(isLowPowerDevice()).toBe(false);
+    expect(sceneTier()).toBe("full");
     expect(isCoarsePointer()).toBe(false);
     expect(isSaveData()).toBe(false);
     expect(isMobileViewport()).toBe(false);
@@ -55,26 +59,80 @@ describe("device hints", () => {
   });
 
   it.each([
-    ["a touch pointer", () => mockMedia(["(pointer: coarse)"])],
     ["reduced motion", () => mockMedia(["(prefers-reduced-motion: reduce)"])],
     ["the data saver", () => mockNavigator({ connection: { saveData: true } })],
     ["four cores", () => mockNavigator({ hardwareConcurrency: 4 })],
     ["two cores", () => mockNavigator({ hardwareConcurrency: 2 })],
     ["4 GB of memory", () => mockNavigator({ deviceMemory: 4 })],
     ["2 GB of memory", () => mockNavigator({ deviceMemory: 2 })],
-  ])("is low power with %s", (_label, arrange) => {
+  ])("shows only the poster with %s", (_label, arrange) => {
     arrange();
-    expect(isLowPowerDevice()).toBe(true);
+    expect(sceneTier()).toBe("static");
   });
 
   it("does not penalize a browser that hides the hardware hints", () => {
     mockNavigator({ hardwareConcurrency: undefined, deviceMemory: undefined });
-    expect(isLowPowerDevice()).toBe(false);
+    expect(sceneTier()).toBe("full");
   });
 
   it("keeps 8 GB and 6 cores on the full path", () => {
     mockNavigator({ hardwareConcurrency: 6, deviceMemory: 8 });
-    expect(isLowPowerDevice()).toBe(false);
+    expect(sceneTier()).toBe("full");
+  });
+});
+
+describe("sceneTier(): one case per row of the decision table", () => {
+  it("row 1: no navigator (server) -> static", () => {
+    const original = Object.getOwnPropertyDescriptor(globalThis, "navigator");
+    Object.defineProperty(globalThis, "navigator", {
+      configurable: true,
+      value: undefined,
+    });
+    try {
+      expect(sceneTier()).toBe("static");
+    } finally {
+      if (original) Object.defineProperty(globalThis, "navigator", original);
+      else Reflect.deleteProperty(globalThis, "navigator");
+    }
+  });
+
+  it.each([
+    ["reduced motion", [TOUCH, "(prefers-reduced-motion: reduce)"], {}],
+    ["the data saver", [TOUCH], { connection: { saveData: true } }],
+  ])("row 2: a capable phone with %s -> static", (_label, media, hints) => {
+    mockMedia(media);
+    mockNavigator({ hardwareConcurrency: 8, deviceMemory: 8, ...hints });
+    expect(sceneTier()).toBe("static");
+  });
+
+  it("row 3: 4 cores with plenty of memory -> static even with a mouse", () => {
+    mockNavigator({ hardwareConcurrency: 4, deviceMemory: 8 });
+    expect(sceneTier()).toBe("static");
+  });
+
+  it.each([
+    ["8 cores and 4 GB", { hardwareConcurrency: 8, deviceMemory: 4 }, "lite"],
+    ["8 cores and 2 GB", { hardwareConcurrency: 8, deviceMemory: 2 }, "static"],
+    ["5 cores", { hardwareConcurrency: 5 }, "static"],
+    ["6 cores and 4 GB", { hardwareConcurrency: 6, deviceMemory: 4 }, "lite"],
+    [
+      "no hints reported",
+      { hardwareConcurrency: undefined, deviceMemory: undefined },
+      "lite",
+    ],
+  ])("row 4: touch with %s -> %s", (_label, hints, tier) => {
+    mockMedia([TOUCH]);
+    mockNavigator(hints);
+    expect(sceneTier()).toBe(tier);
+  });
+
+  it.each([
+    ["8 cores and 4 GB", { hardwareConcurrency: 8, deviceMemory: 4 }, "static"],
+    ["8 cores and 8 GB", { hardwareConcurrency: 8, deviceMemory: 8 }, "full"],
+    ["5 cores and no memory hint", { hardwareConcurrency: 5 }, "full"],
+  ])("row 5: mouse with %s -> %s", (_label, hints, tier) => {
+    mockNavigator(hints);
+    expect(sceneTier()).toBe(tier);
   });
 });
 
@@ -162,6 +220,41 @@ describe("the software WebGL verdict kept for the session", () => {
   });
 });
 
+describe("the slow scene verdict kept for the session", () => {
+  beforeEach(() => sessionStorage.clear());
+  afterEach(() => {
+    jest.restoreAllMocks();
+    sessionStorage.clear();
+  });
+
+  it("is unknown until someone remembers it, then known for the rest of the session", () => {
+    expect(isKnownSlowScene()).toBe(false);
+
+    rememberSlowScene();
+
+    expect(isKnownSlowScene()).toBe(true);
+    expect(sessionStorage.getItem("scene-slow")).toBe("1");
+  });
+
+  it("ignores any other value in the key (only the verdict this module writes counts)", () => {
+    sessionStorage.setItem("scene-slow", "0");
+
+    expect(isKnownSlowScene()).toBe(false);
+  });
+
+  it("counts a blocked sessionStorage as unknown, and remembering then does not throw", () => {
+    jest.spyOn(Storage.prototype, "getItem").mockImplementation(() => {
+      throw new DOMException("blocked", "SecurityError");
+    });
+    jest.spyOn(Storage.prototype, "setItem").mockImplementation(() => {
+      throw new DOMException("blocked", "SecurityError");
+    });
+
+    expect(isKnownSlowScene()).toBe(false);
+    expect(() => rememberSlowScene()).not.toThrow();
+  });
+});
+
 describe("isWebKit (the only engine that needs the showcase video to play once)", () => {
   const iphone =
     "Mozilla/5.0 (iPhone; CPU iPhone OS 17_5 like Mac OS X) AppleWebKit/605.1.15 (KHTML, like Gecko) Version/17.5 Mobile/15E148 Safari/604.1";