Counter ASIC 2.0 status 21:23: the era package, the V3_CLASS composition rule

docs/plans/counter-asic-2-status.md

@@ -325,3 +325,9 @@ Reading: on Apple the added form costs 7 to 17% of the rate for four extra loads
 21:22. PC 1: the 0.3.10 installer build job (job-fb-installer-pc1) FAILED at 21:20:05Z, exit 2 after 2 s (the script, not the build); the shipper is asked to republish within 5 minutes or yield PC 1 to the hot-table measurement (10 min) and follow it. PC 2: agg-cost-pc2-1 still running at 21:21.
 
 21:23. The shipper republished the installer build as fb-installer-pc1-2 (the first exit 2 was Test-Path on a \\wsl$ root path refused to the non-elevated session; the engine is now copied out with wsl -u root), cap 25 min, so PC 1 is the build's until about 21:50; the AMD presence probe (10 s, nothing held) runs beside it. Then: the hot-table job, the era job, the 5090 power sweep, Ember's build and fetches, the repro re-run, the AMD sweep (26 min), Ember's run (25 min).
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+## 21:23 the era package is ready; the V3_CLASS composition rule
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+ca2-era PC 1 package: ~/Desktop/igneum-ca2-era-pc1.zip sha256 f26f997602d94b0a408a6974ee484a7b3249ce18dc91dc00783aa9754e5ff040 (workers 5dd3bc16... and 9615efb3... from ca2-era on ca2-v3 464d6e1 with the pack-loop packfile.h merge and the host.c mh_word fix; packs v2 and era-0 to era-5, the six as class v3 chain packs, generator 3, program id 6b02c7c49eb126bd shared, width 4 B, the same devnet epoch seed and day); fetch-ca2-era-20261005; relay/playbooks/ca2-era-pc1.ps1 (the 5090 then gfx1201, gfx1036 fallback; 6 to 10 min). Mac bit-exactness on these packs: Metal 6/6, Apple OpenCL 6/6 (same fingerprints), CUDA CPU emulation 6/6. Its go follows the hot-table job, about 22:00.
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+Composition rule for the integration (three branches define V3_CLASS): V3_CLASS = LoadClass::MX4's fields (v2 loads, mixer_mult 4, growth on) + era: None (drawn per program inside generate_from_seed_bytes_program_class from the era bytes, LoadClass::era(V3_CLASS, era, &V3_ALLOWED)) + hot: None until the PC rows decide layer 5; the layout rides with the program (program.class.layout() in the interpreter and Epoch::dataset_word), so one day cache (chain_dataset_day) serves every era. The era agent rebases onto ca2-v3 HEAD with that literal; the node agent takes it into the integration tree. The era stream is seeded from "igneum-era/" || E_n (the index dropped: E_n commits to n through the VDF input); the spec text in era-layout.md says so.