conformance: wizer-pre-initialize the composed leg's suite

[lannbot]

Takes the wizer item from #372, corrected by measurement — the item's premises needed inverting in two places, and the payoff concentrates in one leg:

• The composed artifact is NOT wizen-able with the shipped bin (the issue assumed it was the only wizen-able one): component-test wizen on the wac plug output fails with wasmtime-wizer's "nested components with modules not currently supported". The route that works is the reverse order: wizen the bare suite, then compose. The bare suite's polymorph:webcrypto/* imports put it past the shipped plain-suite bin, so ct-driver — which already owns exactly the right linker — grows a --wizen <out.wasm> mode calling component_test_runner::wizen::wizen_with with the same store data and full-support LinkOptions its run path uses (the wizer cargo feature on component-test-runner; wasmtime-wizer 47 matches the tree's wasmtime 47.0.2).
• run-wasmtime and the mutants oracle gain nothing (the issue projected "collapse to seconds" / "sequential ~4x"): both run through ct-driver, whose default is cases_per_instance: 0 — instance-per-worker — so the enumeration tax wizer removes is already amortized there (measured: the full shared suite runs in 2.6s locally at --jobs 8; its ~50s on CI is phase contention). They are deliberately left unchanged.
• run-composed is where K=1 lives: the generic ct-runner's fresh-instance-per-case default pays the suite's registry construction per case, 19k times — and post-conformance: stripe the polyengine-deno leg across Deno Web Worker shards #399 this leg is the conformance phase's tail (finished at +296s in run 32659451264's parallel phase). Wizening keeps the per-case isolation and removes the construction: measured locally (18 cores, --jobs 8), 27.8s → 11.9s wall and 197.9s → 73.3s total CPU (~2.6x); on the CPU-bound 4-vCPU runner the leg's demand drops proportionally, which should take it off the critical path and return the freed share to the other legs. The residual per-case cost is the census handle lift, which is the price of the isolation and stays.

The wizen step runs inside run-composed (0.2s locally): ct-driver --wizen → wac plug the wizened suite → ct-runner unchanged. --suite-artifact still names the canonical bare artifact, so envelope identity, tags scheduling, and the aggregate's lock binding are untouched.

Verification: wizened and unwizened composed runs are row-identical including order (19,093 lines, duration-ms stripped); just conformance-ct::all green (8 targets / 76,364 results and 7 / 2,316, 0 failing beyond declared expected-fail, 0 validation errors — committed matrices unchanged); just test (20 suites), just fmt-check, just clippy pass.

Part of #372 (the artifact-cache-key residue item remains; this PR closes out the wizer item with the leg-level corrections above recorded on the issue).