Three-task decomposition of #166 (sweep a loaded blueprint): the parser
(parse_sweep_blueprint_args + SweepBlueprintArgs + --axis i64-then-f64 lexing),
the member-build (run_blueprint_sweep — a structural mirror of stage1_r_sweep_family
with three deviations: by-name axes, reload-per-member since Composite is !Clone,
per-member topology_hash) + the .json dispatch arm, and the tests (grammar +
equivalence-vs-run_signal_stage1r + the binary sweep-family E2E + unknown-axis
fail-clean). Purely additive; reuses the engine sweep machinery + cycle-1's
wrap_stage1r unchanged. Grounding decisions (Q1-Q5) recorded on #166.
refs #166
Brummel
b6d4ebfe23