A data-level author can now discover a loaded blueprint's open sweepable knobs
before sweeping: `aura sweep <blueprint.json> --list-axes` prints one
`<name>:<kind>` line per open knob, in param_space() order, then exits 0. Before
this the only way to learn the names was to guess a `--axis` and read the
MissingKnob/UnknownKnob error — which names only the rejected knob, never the
valid set. Prerequisite for #173 (IS-refit walk-forward must know which axes to
re-fit per in-sample window).
Design (derived, recorded on #169): the query lands on the SWEEP verb, not
`graph introspect`, because the accepted axis names are produced by the sweep's
own harness-wrapping (wrap_stage1r nests the loaded signal as a
BlueprintNode::Composite named "stage1_signal", so collect_params prefixes them
— stage1_signal.fast.length, not the raw fast.length). Only the sweep verb owns
that wrapping. A new blueprint_axis_probe helper single-sources the wrapped
probe and now subsumes the two previously-inline copies (blueprint_sweep_family
+ blueprint_mc_family), so listed == swept by construction (and stays so across
#159's harness retirement) — no second source of truth.
--list-axes is a standalone query (valueless flag handled before the per-flag
value-consume; rejected with exit 2 if combined with any other flag). A closed
blueprint prints nothing (exit 0). A malformed blueprint is rejected at the
existing dispatch boundary (exit 2, UnknownNodeType), never a panic.
Tests: unit blueprint_axis_probe (prefixed names + empty for closed) + unit
parse grammar (standalone), and five cli_run E2Es — prints names, closed-empty,
rejects-other-flags, malformed-safety (no panic), and a round-trip that DERIVES
the names from --list-axes and feeds them back into a working sweep (pins the
listed==swept invariant #169 exists to close). Verified myself: cargo build
--workspace, cargo test --workspace, cargo clippy --workspace --all-targets -D
warnings all green; no regression in the refactored sweep/mc probes. Engine and
registry untouched (invariants 1/8/9).
closes#169
Brummel
bd2003e217