LB_DIFF_VAR_CQL_BASE=297, LB_SAMPLE_VAR_CQL_BASE=301,
LB_DIFF_VAR_C51_BASE=305, LB_SAMPLE_VAR_C51_BASE=309. Bumps SP5_SLOT_END
297 → 313 and SP5_PRODUCER_COUNT 123 → 139. Helper fns mirror the
existing budget_*/flatness/q_var_per_branch pattern. Layout fingerprint
extended. slot_layout_no_overlaps_and_total_correct asserts the new
total.
Audit doc Fix 31 stub added; will be extended commit-by-commit through
Tasks 2-9 of the SP7 plan.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>