ci: quick-tier Σ-executed step recompiles the tree-reader graph (reuse step 22's build) #5922

Measured (handoff/aprender-cop/ci-timing-1022/shard-sections.md): the Σ-executed step's second cargo nextest list prints a 1.7-4.8 min (median 2.1) Finished test profile in all 12 sampled workspace-test-shard jobs, 21 workspace crates recompiled. Cause: the run step builds -p … --lib --bins --test NAME… (ci_test_tier.sh --build-flags) while the list builds -p … --lib --tests (every test target, different units). Fix: list with the same build flags. Acceptance: same test ids listed/executed before and after; same profile and features.