Drop the Dataset Statistics section when no chart actually renders

[adityasingh2400]

Closes #378.

The section already had a guard meant to collapse it when there is nothing to show, but it counted appended parts instead of appended content. The channel count and sampling frequency renderers are appended unconditionally once their has_ flag is set, and _make_count_bar_chart returns an empty string when the entries it was handed carry no usable val. That empty append still grew parts, so len(parts) <= 1 was False and the page kept a Dataset Statistics heading above an empty cohort grid.

Testing the joined content instead makes the section collapse for a dataset with no usable subject, age, channel count or sampling frequency metadata, which is the case in the issue. The change is one line in _format_recording_stats_section plus a comment explaining why it tests content rather than length.

The issue body is empty, so I traced the symptom to the code rather than working from a description. Added tests/test_dataset_page_stats.py with six cases, following the section_module fixture pattern already used by test_dataset_page_electrodes.py. Three of them fail on develop, and the failure diff prints exactly the reported symptom, a Dataset Statistics heading followed by an empty eegdash-ed-cohort-grid. The other two go the other direction, checking that a dataset with real channel counts or a real duration still renders, so the guard does not overcorrect.

After the change, 11 pass, my 6 plus the 5 existing dataset_page tests. The repo's own pre-commit ruff args pass clean and ruff format --check reports both files already formatted.

Disclosure: this change was prepared with AI assistance. I have reviewed and tested it.

[adityasingh2400]

Two things about the red here, and the second one is a problem with my own PR rather than with CI.

The failures are a network outage, not this change. All 21 in test (ubuntu-latest, 3.12) are ConnectTimeout against data.eegdash.org, for example:

requests.exceptions.ConnectTimeout: HTTPSConnectionPool(host='data.eegdash.org', port=443):
Max retries exceeded with url: /api/eegdash/count
(Caused by ConnectTimeoutError(..., 'Connection to data.eegdash.org timed out. (connect timeout=30)'))

docs (ubuntu-latest, 3.12) fails for the same reason, one layer up: sphinx_gallery.gen_gallery raises ExtensionError from that same timeout during builder-inited, so make html never gets to render anything. This PR touches _format_recording_stats_section, which does no network access, and the run took 2 hours 28 minutes, almost all of it in connect timeouts.

The part worth acting on: my tests are not running. The job reports

SKIPPED [1] tests/test_dataset_page_stats.py:22: dataset_page extension requires sphinx

so the 106 lines I added are skipped in the test job, which does not install sphinx, and the docs job builds documentation rather than running pytest. That means this PR currently has no CI coverage at all for the behavior it changes, which is not what I intended when I added the file.

I would rather fix that than leave a test that only ever passes locally. Before I pick an approach, which would you prefer:

1. Drop the sphinx dependency from the test by exercising _format_recording_stats_section directly with plain dictionaries, so it runs in the ordinary test job.
2. Add sphinx to the test environment so the existing test executes as written.
3. Leave it skipped, if the docs extension is deliberately outside the unit test scope here.

Happy to implement whichever fits how you want this directory covered.

[adityasingh2400]

Went with option 1 since it is the only one that needs nothing from you, and leaving the file skipped meant this PR had no coverage at all. Say the word if you would rather have option 2 or 3 and I will switch.

sections.py touches sphinx exactly once, LOGGER = logging.getLogger(__name__) against sphinx.util.logging, and the functions under test never log. So instead of skipping, the module now stands in a stdlib logger when sphinx is absent. The code under test is untouched.

Verified in a venv built the way the test job builds one, pip install -e . with no doc extras: 6 passed. With sphinx installed it is also 6 passed, so the docs path is unaffected. Reverting sections.py to the pre-fix version fails 3 of the 6, so the coverage is real rather than vacuous.

One thing you may want to look at separately: tests/test_dataset_page_electrodes.py uses the same pytest.importorskip("sphinx") line, so it is also being skipped in the test job today. I left it alone since it is outside this PR, but it is the same gap.

The 21 ConnectTimeout failures are unrelated and still present. data.eegdash.org is still refusing connections as of a few minutes ago, TCP never establishes.