E2E: a lane where every @requires-gpu scenario resolves to skip should be flagged, not reported ok

Context

Came up during PR #377's review (moving Strix Halo Ubuntu/Windows to the DevLab Dispatch pool). An earlier review pass suggested making the Windows lane's GPU preflight fail-closed (error instead of exit 0) when rocm-smi is absent, to stop a lane silently reporting PASS with zero real GPU scenarios executed. That specific fix is wrong: rocm-smi is absent on the existing static Windows host too (confirmed against the 2026-09-09 nightly log), so a fail-closed preflight would red both Windows lanes on hardware that's demonstrably fine.

The actual gap

The real hole isn't the preflight, it's reconciliation. Confirmed by reading the code:

• tests/e2e-cucumber/tests/e2e.rs:1225 filters Expectation::Skip out before running scenarios.
• :1348 only exits 1 on unexpected_fail/stale_xpass.
• tests/e2e-cucumber/src/expectation.rs:433 resolves @requires-gpu to skip when there's no GPU.
• crates/e2e-report/src/lib.rs:981 renders pass=0, skip=N as ok().

So a lane whose GPU detection is broken (or that never had a GPU at all) exits 0 and shows green in the consolidated grid — identical to a lane that actually exercised every scenario. Nothing distinguishes "everything passed" from "everything was skipped."

Suggested direction

A portable check that works on any lane, not just Windows: when the capability probe (platform.json) reports the host has an AMD GPU, but every @requires-gpu scenario in that run resolved to skip, treat that as a problem (exit non-zero / flag in the consolidated report) rather than ok. This doesn't depend on rocm-smi specifically or any one platform's tooling, and it catches the actual failure mode (a lane that silently stopped testing anything) without false-positiving on hardware that's fine but lacks a particular diagnostic tool.

Not urgent/blocking anything — a robustness improvement for the E2E harness's reconciliation logic.

Start with tests/e2e-cucumber/tests/e2e.rs around lines 1225 and 1348, then read tests/e2e-cucumber/src/expectation.rs:433 and crates/e2e-report/src/lib.rs:981. Trace how platform.json capability data and @requires-gpu scenario results are reconciled. Done means a GPU-reported lane with all such scenarios skipped is flagged non-zero or visibly non-ok, while a lane without a GPU remains unaffected.