Update imported {standalone} scripts to current source

The standalone scripts imported from [`insightsengineering/standalone`](https://github.com/insightsengineering/standalone) have drifted from the current source (`main`) and should be refreshed via `usethis::use_standalone()`.

Current drift in `pager` (vs standalone `main`):

| Imported file | pager `last-updated` | standalone `main` | changed lines |
|---|---|---|---|
| `import-standalone-check_pkg_installed.R` | 2025-02-03 | 2025-10-03 | ~88 |
| `import-standalone-checks.R` | 2025-05-08 | 2025-05-08 | up to date |
| `import-standalone-cli_call_env.R` | 2024-04-10 | 2024-04-10 | up to date |
| `import-standalone-purrr.R` (from `r-lib/rlang`) | — | — | not in scope |

Refreshing keeps the shared check/utility helpers consistent across the ecosystem (`cards`, `cardx`, `crane`, `pager`).

Start with import-standalone-check_pkg_installed.R and compare it with the current main source in insightsengineering/standalone. Use usethis::use_standalone() to refresh the drifted standalone script, leaving the up-to-date checks and cli_call_env imports unchanged. Done means the imported helper matches the standalone source and the recorded last-updated metadata is current.

Written by the indexing model from the issue text.