Update doc switcher & readme doc

[leehart]

Re: issue #843

[leehart]

Noting linting failure here, which was addressed in draft PR #842

• https://github.com/malariagen/malariagen-data-python/actions/runs/21061650460/job/60569151449?pr=844

malariagen_data/anoph/sample_metadata.py:1158: error: Name "pd.core.series.Series" is not defined [name-defined]
Found 1 error in 1 file (checked 98 source files)

I'll transfer the linting fixes from #842 to here as required.

[leehart]

Noting random test failure:

=========================== short test summary info ============================
FAILED tests/anoph/test_snp_frq.py::test_allele_frequencies_advanced_with_area_by[adir1_sim-country] - ValueError: No SNPs remaining after applying variant query "effect in ['NON_SYNONYMOUS_CODING', 'START_LOST', 'STOP_LOST', 'STOP_GAINED']".
=========== 1 failed, 900 passed, 333 warnings in 1088.05s (0:18:08) ===========

[leehart]

Noting random failure during coverage tests:

=========================== short test summary info ============================
FAILED tests/anoph/test_cnv_frq.py::test_gene_cnv_frequencies_with_max_coverage_variance[ag3_sim-1] - Failed: DID NOT RAISE <class 'ValueError'>
=========== 1 failed, 900 passed, 315 warnings in 1946.95s (0:32:26) ===========

• https://github.com/malariagen/malariagen-data-python/actions/runs/21061927392/job/60570034669?pr=844

[leehart]

All CI checks have passed on this PR, for the time being. Ready for review.