test(ui): stabilize host selection mock and cross-platform test runners

packages/ui/test/markdown-viewer.test.tsx

@@ -205,10 +205,10 @@ describe("qitem-markdown-bare-marker-loop — parser terminates on a bare list m
     const { spawn } = await import("node:child_process");
     const path = await import("node:path");
     const childScript = path.resolve(import.meta.dirname, "fixtures/markdown-bare-marker-child.tsx");
-    const runner = path.resolve(import.meta.dirname, "../../../node_modules/.bin/tsx");
+    const tsxCli = path.resolve(import.meta.dirname, "../../../node_modules/tsx/dist/cli.mjs");
 
     const outcome = await new Promise<{ code: number | null; signal: string | null; killed: boolean; out: string; err: string }>((resolve) => {
-      const child = spawn(runner, [childScript], {
+      const child = spawn(process.execPath, [tsxCli, childScript], {
         cwd: path.resolve(import.meta.dirname, ".."),
         // Low heap so a runaway parser dies fast instead of eating the box.
         env: { ...process.env, NODE_OPTIONS: "--max-old-space-size=256" },

packages/ui/test/mh2-host-level.test.tsx

@@ -689,7 +689,7 @@ describe("rev1-r2 B1/B2 — remote action gates (topology table / terminal grid
   });
 
   it("seat page remote (B1+B2): host-keyed detail fetch, NO bare local URL, actions row read-only, inline terminal gated, ZERO POSTs", async () => {
-    wireB1Fetch();
+    wireB1Fetch("vps-a");
     renderPrimed(() => <LiveNodeDetails rigId="r1" logicalId="a1" />, "vps-a");
     await waitFor(() => expect(screen.getByTestId("live-node-actions-remote-readonly")).toBeTruthy());
     // B1: no local action affordances, terminal honestly gated

packages/ui/test/slice-20-mobile-density.test.tsx

@@ -31,7 +31,7 @@ describe("slice 20: FilesWorkspace responsive two-pane shape", () => {
   it("/files route mounts FilesWorkspace instead of falling through to Not Found", async () => {
     const source = await readSource("src/routes.tsx");
     expect(source).toMatch(/import \{ FilesWorkspace \} from "\.\/components\/files\/FilesWorkspace\.js";/);
-    expect(source).toMatch(/path: "\/files",\n\s+component: FilesWorkspace/);
+    expect(source).toMatch(/path: "\/files",\r?\n\s+component: FilesWorkspace/);
   });
 
   it("outer container uses flex-col on mobile + sm:flex-row on desktop", async () => {