chore: remove samUrl prop from IgvBrowser (igv.js only supports BAM)

refactor: require native samtools/minimap2, delete hand-rolled BAM/BAI code

fix: igv.js fetch BAM/BAI as Blobs, client-side SAM-to-BAM conversion, proper BGZF

fix: SAM-only igv.js track, indexed:false reference, debug logging

fix(ngs): dynamic locus + SAM-first igv.js for reliable genome browser

feat(ngs): pure-Python SAM to BAM converter with BGZF + BAI index for igv.js

fix: load igv.js from CDN instead of ESM import

fix: igv.js white screen — CIGAR ops, qual strings, locus format

feat: add igv.js genome browser + proper 6-step NGS pipeline