v0.1.2: Correctness fixes for the ClinVar significance filter, dual-callset frequency rows, and the LOEUF interval render

Correctness fixes for the ClinVar significance filter, dual-callset frequency rows, and the LOEUF interval render

Fixed:

• gnomad_search_clinvar — clinical_significance enforced post-fetch; the NCBI field tag leaked non-matching classifications, and the whole-word match now composes with min_review_stars (#2)
• gnomad_list_gene_variants — exome|genome rows report joint AN (sum across callsets) and joint AF (recomputed from ac/an); max_af filters the joint frequency (#3)
• gnomad_get_gene_constraint — content[] LOEUF interval upper bound renders oe_lof_upper, not the oe_lof point estimate (#5)

94 tests pass; bun run devcheck clean.