feat(web): view transitions on route changes; content enter animation

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

apps/web/src/nav.test.ts

@@ -19,3 +19,16 @@ test("features.ts imports only browser entries, by package name", () => {
   for (const s of specs) expect(s === "@stc/contracts" || /^@stc\/feature-[a-z]+\/web$/.test(s)).toBe(true);
   expect(specs.filter((s) => s.endsWith("/web")).length).toBe(4);
 });
+
+test("changesPage: a view transition for a new kind of page, none between steps of the same page", async () => {
+  const { changesPage } = await import("./nav");
+  const routes = webFeatures.flatMap((f) => f.routes.map((r) => ({ path: r.path })));
+  expect(changesPage(routes, "/", "/c/sample")).toBe(true);
+  expect(changesPage(routes, "/c/sample", "/c/sample/m1-intro")).toBe(true);
+  expect(changesPage(routes, "/c/sample/m1-intro", "/c/sample/notes")).toBe(true);
+  expect(changesPage(routes, "/c/sample/m1-intro", "/c/sample/m1-code")).toBe(false);
+  expect(changesPage(routes, "/c/sample/m1-intro", "/c/other/x?t=3")).toBe(false);
+  expect(changesPage(routes, "/c/sample/m1-video", "/c/sample/m1-video?deck=d1&slide=2")).toBe(false);
+  expect(changesPage(routes, "/c/a%20b/x", "/c/a%20b/y")).toBe(false);
+  expect(changesPage(routes, "/c/sample", "/nowhere/at/all/deep")).toBe(true);
+});