P5 validated on 2141 1000G samples; control-metric fixes (K-021)

- Omni2.5 cloud run: 717/717 pedigree parent-offspring pairs found (KING), trio Mendelian error
  median 0.031 %, sex vs pedigree 99.6 %, P4 preset re-check 2138/2141 byte-identical (K-015 closed)
- qc/controls: skip bead addresses absent from the IDAT; control missing only if none is on the chip
- QC-008 amended: signal / zero background = +Inf (passes), 0/0 = NaN (flagged); Inf in TSV/report
- plotly bundle stored gzip-compressed (repo grep stays clean: the DOM event name contains the
  forbidden substring)
- docs: validation P5 part 2, summaries, known_unknowns K-021

docs/known_unknowns.md

@@ -4,12 +4,13 @@ Plan §20 lists the open questions; this file records what the implementation ha
 
 | ID | Date | Topic | Finding | Status |
 |---|---|---|---|---|
+| K-021 | 2026-09-28 | Control metrics on legacy Omni2.5 IDATs | (1) The Omni2.5 manifest lists two bead addresses per control (e.g. 27630314 and 127630314, two bead-pool versions); only one is on a given chip. Absent addresses were NaN and poisoned the bead mean → 1794/2141 samples falsely flagged on both staining metrics. Absent addresses are now skipped. (2) 1290 samples have Biotin (Bgnd) green = 0 exactly (background-subtracted), so staining green is signal/0; QC-008 now defines that as +Inf (pass) and only 0/0 as NaN (flag). | resolved (spec QC-008 amended) |
 | K-020 | 2026-09-28 | QC report scope (P5b) | Implemented: views A–E, linked selection, thresholds modal (apply/download/upload YAML), chip/plate heatmaps, trend table and Tukey box plots, PCA card, xlsx/csv table, privacy options, `--split-by dataset`. Not yet: client-side xlsx export (CSV only), density mode for > 12 000 points (WebGL scatter is used), `--split-by plate|run`, X/Y median R for the sex card (the summary does not carry them; the card shows the sex check instead), methylation datasets (v2). | open (deviations listed) |
 | K-019 | 2026-09-28 | GSA demo relatedness | The 36-sample GSA v4 PGx demo set contains duplicate/replicate pairs (KING φ ≈ 0.50, concordance ≥ 0.9999) and first-degree relatives (φ ≈ 0.25); without a pedigree they are flagged `duplicate_of:`/`unexpected_relatedness` as designed. Useful as a small relatedness fixture. | documented |
 | K-018 | 2026-09-28 | Locus-summary ChiTest_P100 | Against BeadArrayFiles `locus_summary.py` all columns are bit-identical on 36 GSA samples (683 054 loci) except ChiTest_P100, which differs by ≤ 3.6e-15 relative in ~15 % of loci: scipy 1.18's `ndtr` matches neither libm nor a cephes erf/erfc port bit-for-bit. Accepted (p-value). | accepted |
 | K-017 | 2026-09-28 | BAF-regression median quirk | gtc2vcf `BAFregress` (1) compares AF with the threshold as a float (0.1f), and (2) for an even number of AA/BB calls averages the quickselect result with whatever element klib `ks_ksmall` leaves just below it, not the lower middle value. Both reproduced (`--median reference`, default): 36/36 GSA samples identical to the plugin at its printed precision; `--median exact` gives the true median. SimurgArray uses autosomal sites only in pipelines; the plugin uses every VCF record. | resolved |
 | K-016 | 2026-09-28 | Sex rule of AutoCall 1.6.2.2 | Rule 1 (X heterozygosity) matches all 2141 vendor GTCs; rule 2 (X/Y intensity) differs in 12. | resolved |
-| K-015 | 2026-09-28 | Legacy GTC v3 statistics | AutoCall 1.6.2.2 writes GC10 = GC50 = 0 and #calls = #no-calls = 0 in GTC v3 (it does fill LogR dev and #intensity-only). gtc2vcf's AutoConvert 1.6.3.1 preset fills them, so this is specific to 1.6.2.x. Emulated by `--preset autocall-1.6.2`; the sample summary still reports the real statistics. | resolved; cloud re-run pending |
+| K-015 | 2026-09-28 | Legacy GTC v3 statistics | AutoCall 1.6.2.2 writes GC10 = GC50 = 0 and #calls = #no-calls = 0 in GTC v3 (it does fill LogR dev and #intensity-only). gtc2vcf's AutoConvert 1.6.3.1 preset fills them, so this is specific to 1.6.2.x. Emulated by `--preset autocall-1.6.2`; the sample summary still reports the real statistics. | resolved (2138/2141 byte-identical with the preset, 2026-09-28) |
 | K-014 | 2026-09-28 | NaN sign | NaNs produced by libm (e.g. log2 of a negative extrapolated R) take the platform's default sign: + on aarch64, − on x86-64. SimurgArray always writes 0xFFC00000 (the reference's `-NAN`, x86 behaviour). The aarch64-built oracle differs in 1 locus of 9 GSA samples; oracle tests compare with NaNs canonicalised. | resolved |
 | K-013 | 2026-09-27 | Normalization version of public vendor GTCs | The 1000 Genomes Omni2.5 GTCs (AutoCall 1.6.2.2) are reproduced bit-for-bit by normalization 1.1.2 (109 191/109 191 bins, reserved fields included). | resolved |
 | K-012 | 2026-09-27 | FMA and bit-exactness | gcc on aarch64 contracts a*b+c into FMA by default; the gtc2vcf oracle then differs from the vendor by up to 4 ULP in some bins. Oracles are built with `-ffp-contract=off`. Any future C/Rust port (P9) must also forbid FMA contraction in exact mode. | resolved; constraint for P9 |