pv shapes: the LONE-contract venue declines with no report — by_shape and declines exist only on the directory path #3648

Found by a quorum lane re-reviewing #3622 (#3610 arm 1). Not a regression — an asymmetry #3622 made visible by fixing one half of it.

The two venues answer differently

decline() asks the vacuity question globally:

// crates/aprender-contracts/src/lint/shapes_gate.rs:349
if report.focus_nodes_n == 0 {
    return Some(ShapesOutcome::NoFocus { shapes_n });
}

and that returns before the result path builds by_shape, declines and armed_shapes. NoFocus then renders through skipped_gate("shapes", …) with Vec::new() findings and no extra (lint/mod.rs:772).

Why it matters, and why it is P1 and not P0

The report requirement is not decoration. From #3622's own test file:

"Downstream consumers (infra's SLK gate) capture stdout and parse it REGARDLESS of exit code, because pv already exits non-zero on Fail. A refusal that printed only a bare decline: line would read to them as 'no by_shape' and score UNMEASURED — indistinguishable, from their side, from a broken pv."

That is precisely what the lone venue does today.

It is P1 because the consumer that motivated the requirement runs pv over a DIRECTORY, which is the venue that now carries the report. A lone-file invocation is a developer running pv lint <file>, where the bare decline is legible on a terminal. So this is a real inconsistency with a bounded blast radius, not a live scoring defect.

done_when

1. The lone venue emits the same evidence document as the directory venue: by_shape, declines, and a verdict of Unknown(NoFocus), on the exit-2 path.
2. This requires building the report before decline() is consulted, or threading it through ShapesOutcome — a restructure of the outcome path, which is why it was not folded into #3610: a shapes gate reported Pass over ZERO focus nodes — the vacuity check was global, so a directory hid it #3622.
3. shapes_vacuity.rs::the_lone_contract_venue_declines_without_a_report_and_that_is_recorded currently asserts r.extra().is_null() and carries an instruction in its own failure message: when this lands, delete that test and add json-missing-ref to the_three_answers_remain_distinct's report loop — do not loosen the assertion to keep it green.
4. Falsifier both ways: the lone venue gains a parseable report, and the directory venue keeps hers.

How it was hidden

#3622's tests asserted the report requirement for the directory venue and not for the lone one — the_lone_contract_venue_still_declines_as_it_always_did checked only code != 0, and the_three_answers_remain_distinct omitted json-missing-ref from the loop that asserts a parseable report. Two tests that together covered one venue's requirement and quietly not the other's: the same half-checked shape #3610 was about, inside the fix for it.

Refs #3610, #3622