GitHub Pages has been unreliable for the eval sites, so they now also
deploy to Vercel at `https://stagehand-eval-sites.vercel.app/`. This PR
swaps the host. Paths are unchanged:

```
https://browserbase.github.io/stagehand-eval-sites/sites/<name>/…
https://stagehand-eval-sites.vercel.app/sites/<name>/…
```

**What changed (76 files)**
- Every `browserbase.github.io/stagehand-eval-sites/` URL across evals
tasks, sdk-ts tests, the TS/Python/Go examples and the docs is now the
Vercel URL. `git grep 'github\.io/stagehand-eval-sites'` matches only
`get_url.ts`.
- `packages/evals/core/tasks/page-info/get_url.ts` stored the host as an
escaped regex. Its allowlist now accepts both hosts.
- oxfmt reflowed lines where the shorter URL now fits on one line. Apart
from `get_url.ts`, each file matches `main` once the host is normalized
and whitespace and commas are ignored.

**Verified against the Vercel host**
- All 114 files under `sites/` are byte-identical to Pages (sha256) with
matching content types.
- All 83 site directories redirect from `/sites/x` to `/sites/x/`, as on
Pages.
- All 59 referenced URLs return 200, and repo files outside `sites/` are
not served.
- In Browserbase sessions, the final URL, title, visible text length and
out-of-process iframe count match Pages for every page tested. The OOPIF
fixtures, whose child frames stay on `seanmcguire12.github.io`, still
produce a separate-process iframe target; the same-origin iframe
fixtures still don't.

**Related:** browserbase/stagehand-eval-sites#80 (Vercel config) and
browserbase/stagehand-eval-sites#81 (self-links made relative, so the
`ionwave` URL assertion holds on either host).

GitHub Pages stays up, so older commits and published examples keep
working. To roll back, revert this PR.

<!-- This is an auto-generated description by cubic. -->
---
## Summary by cubic
Points eval sites at Vercel instead of GitHub Pages because Pages has
been unreliable. The host changes from
`https://browserbase.github.io/stagehand-eval-sites/` to
`https://stagehand-eval-sites.vercel.app/`; paths under `sites/` are
unchanged.

**Details**
- Updates every eval-sites URL across evals tasks, sdk-ts/Go/Python
examples and tests, and docs.
- `get_url.ts` now accepts both the old and new hosts, and lines are
reflowed where the shorter URL fits.
- Verified the Vercel host serves byte-identical files with matching
content types, redirects, and 200s for all referenced URLs.
- GitHub Pages stays up, so rollback is just reverting this PR.

<sup>Written for commit 0f51333c3e1664818b872ab007e62c74965e343e.
Summary will update on new commits.</sup>

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**Merge order:** browserbase/stagehand-eval-sites#81 must be merged and
live on Vercel before this PR. `act/ionwave` clicks a link on that page
and asserts the Vercel URL. Without #81, the link still points to GitHub
Pages and the eval fails on every model.