Describe the bug

Since v52.16.0, a deck built for a sub-directory (slidev build --base /sub/) 404s when navigating between slides. Clicking/pressing to the next slide produces a URL with the base doubled, e.g. landing on /<base>/1 and pressing → goes to /<base>/<base>/2, which matches no route and renders Slidev's own "404 — Page //2 not found".

This is a regression introduced by #2562 ("use BASE_URL in getSlidePath for monorepo sub-directory deployments"), which is the only change shipped in 52.16.0 touching packages/client/logic/slides.ts.

Root cause

getSlidePath now returns a base-prefixed path:

// 52.16.0 (after #2562) — packages/client/logic/slides.ts
return `${import.meta.env.BASE_URL}${path}`   // e.g. "/sub/2"

// 52.15.2 (before #2562) — returned a base-LESS path
return presenter ? `/presenter/${no}` : `/${no}`   // e.g. "/2"

But the router history is already created with the base:

// setup/main.ts
createWebHistory(import.meta.env.BASE_URL)   // base = "/sub/"

…and navigation pushes the getSlidePath value as a route path:

// composables/useNav.ts (go)
router.push({ path: getSlidePath(no, isPresenter.value, ...) })

So with --base /sub/, router.push({ path: "/sub/2" }) runs through a history whose base is /sub/, and the base is prepended again → URL /sub/sub/2, route /sub/2 → no match (routes are /:no) → 404. Affects both routerMode: history and hash (in hash mode it's /sub/#/sub/2).

Reproduction

1. Any deck. Set build to slidev build --base /sub/ --out dist/sub.
2. Serve dist with any static server so the deck is at http://localhost:PORT/sub/.
3. Open /sub/, press → (next slide).

Expected: /sub/2 (slide 2).
Actual (52.16.0): /sub/sub/2 → Slidev 404 page. Works correctly on 52.15.2.

Verified with a plain static file server (no edge/host rewrites involved), so this is purely client-side routing.

Reproduction (link)

Minimal: any slidev build --base /sub/ output served at /sub/. Happy to provide a repo if helpful.

System Info

@slidev/cli: 52.16.0 (broken) vs 52.15.2 (works)
routerMode: history (default) and hash both affected

Suggested fix

Either have getSlidePath return a base-less path again (and rely on the history base), or strip the base before router.push in useNav, so the base is applied exactly once.