DOC: keep Hypothesis strategy examples readable

[nightcityblade]

Description

Closes #11465.

The introductory Hypothesis examples now generate variables without arbitrary attributes. This keeps the examples varied while preventing recursively generated metadata from overwhelming the rendered user guide. The later section that explains attribute strategies remains unchanged.

Checklist

• Closes Testing secting is user guide renders incorrectly #11465
• Tests added — N/A; this is a documentation-only rendering change.
• User visible changes (including notable bug fixes) are documented in whats-new.rst — N/A; no runtime behavior changes.
• New functions/methods are listed in api.rst — N/A; no API changes.

AI Disclosure

• This PR contains AI-generated content.
  • I have tested any AI-generated content in my PR.
  • I take responsibility for any AI-generated content in my PR.
    Tools: Codex. I reviewed the complete diff and validated generated examples locally.

[nightcityblade]

CI follow-up: the only failing job completed 21,383 tests and then hit RuntimeError: error during blosc decompression: 0 in TestZarrRegionAuto::test_zarr_region_chunk_partial_offset[2]. This is unrelated to this docs-only change (doc/user-guide/testing.md); all other CI jobs passed. I attempted to rerun the failed job, but contributors do not have permission to rerun upstream workflows, so a maintainer rerun is needed.