The gate reads H2's confirmatory cell on C++ examples against the matched foreign arm¶

decomposition.design(admitted, foreign_source, h2_withdrawn=...) implements item 1 of the plan above: the pair both ways when Qt and Chromium are admitted, otherwise one Qt cell against foreign_source, one of FOREIGN_SOURCES, refused without Qt admitted. No read takes the source from a caller: registered_design reads FOREIGN_SOURCE, set by the commit that fixes the source before the first H2 development contrast, and H2_WITHDRAWN, set if the foreign pool fails check 4, which leaves H1 alone at the whole family level. The gate, both supplements, registered_read and h1_test_gate all read it, so no source can be tried against a contrast and then chosen. Every confirmatory H2 cell reads its organization's C++ examples (H2_POPULATION, filtered lazily through Restricted, so rows of organizations H2 does not read are never parsed) against the arm foreign_arm(source, sibling) names, one per evaluated half (matched_clusters, through paired_clusters). decomposition_gate keeps H1's verdict on every example and takes the joint shares, the sum and H1 restricted to C++ on the C++ examples, labelling each cell and joint reading with its population; exploratory cells are unchanged. whole_hunk_supplement replaces cpp_supplement: the same matched contrast over every example, reported only. An H2 development read also needs H2 bounds, which only the H2 simulation supplies, so none can run yet. The matched sampler and the partition jobs that train the foreign arms are the next step; no H2 contrast has been run.