swarm-ui: move the shell's route layout predicates out and test them

isFullBleedRoute and isWideBodyRoute are plain functions of a path, so
they move from Shell.tsx to shell/routes.ts, where the new tests cover
the start page, the hive directory's move to /hives, the terminal
paths and the wide-body routes.

frontend/packages/swarm-ui/test/routes.test.mjs

@@ -0,0 +1,42 @@
+// The shell's per-route layout: which paths are full-bleed, which get the
+// wide body. Run by `npm test`.
+import assert from "node:assert/strict";
+import { test } from "node:test";
+import { isFullBleedRoute, isWideBodyRoute } from "../src/shell/routes.ts";
+
+test("the start page is full-bleed", () => {
+  assert.equal(isFullBleedRoute("/"), true);
+});
+
+test("the hive directory moved off / and is not full-bleed", () => {
+  assert.equal(isFullBleedRoute("/hives"), false);
+  assert.equal(isWideBodyRoute("/hives"), false);
+});
+
+test("an agent's terminal and a subagent's are full-bleed", () => {
+  assert.equal(isFullBleedRoute("/agents/iris/terminal"), true);
+  assert.equal(
+    isFullBleedRoute("/agents/iris/subagents/scout-1/terminal"),
+    true,
+  );
+});
+
+test("the agents page and other routes are not full-bleed", () => {
+  for (const path of ["/agents", "/agents/iris", "/jobs", "/issues"]) {
+    assert.equal(isFullBleedRoute(path), false, path);
+  }
+});
+
+test("a terminal path with extra segments is not full-bleed", () => {
+  assert.equal(isFullBleedRoute("/agents/iris/terminal/extra"), false);
+  assert.equal(isFullBleedRoute("/agents//terminal"), false);
+});
+
+test("the wide-body routes are exactly the table pages", () => {
+  for (const path of ["/issues", "/agents", "/review-runs", "/review-tryout"]) {
+    assert.equal(isWideBodyRoute(path), true, path);
+  }
+  for (const path of ["/", "/jobs", "/schedules", "/components"]) {
+    assert.equal(isWideBodyRoute(path), false, path);
+  }
+});