feat(engine): open drawElement fast capture to Windows hardware GPU

Widen the default-on drawElement clamp from darwin-only to darwin|win32
(still requiring a non-software-GPU browser). The darwin restriction was a
validation envelope, not an architectural limit — the CanvasDrawElement
Chrome flag ships on every platform, and every safety layer that made the
macOS default-on release (v0.7.38) survivable is platform-neutral:
compile-time gates, the SwiftShader init gate, per-render worker-encode
self-verification with screenshot fallback, and the blank guard. Worst case
on an unvalidated D3D11 backend is the same as on Metal: verify catches a
bad frame and the render re-runs on the screenshot baseline.

Why now: 30-day telemetry shows ~206k non-CI hardware-GPU Windows renders
(~78% of the win32 fleet, 18k installs) held on the slow screenshot path by
the clamp — the second-largest perf population after macOS, carrying ~1,550
capture-hours/month in the DE-eligible >=700-frame band alone at a measured
~2x speedup opportunity.

Instrumentation for the new cohort: drawElement session init now records the
raw WebGL UNMASKED_RENDERER_WEBGL string (detectSwiftShader generalized to
detectGpuBackend — same single evaluate, the string was previously read and
discarded) and threads it session -> CapturePerfSummary -> RenderPerfSummary
-> render_complete as `gpu_renderer`. drawElement damage proved
compositor-backend-specific throughout the macOS rollout, so D3D11-cohort
failures must cluster by ANGLE backend + GPU vendor (NVIDIA/AMD/Intel), not
just `os`.

The two DE clamp branches are extracted into a pure, unit-tested
`resolveDefaultDrawElement` (platform + GPU mode + worker-encode + explicit
opt-in), which also drops resolveConfig's cyclomatic complexity. The win32
streaming-encode compound tests collapse onto one shared helper.

Linux stays excluded: that fleet is headless/Docker SwiftShader, where DE
has no speedup and known rendering defects. Kill switches unchanged:
PRODUCER_EXPERIMENTAL_FAST_CAPTURE=false, --experimental-fast-capture=false.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

packages/cli/src/commands/render.ts

@@ -1102,7 +1102,6 @@ let deParallelRouterTrialFiredThisProcess = false;
  * resetting outside a test process where many independent test cases share
  * one imported module instance.
  */
-// fallow-ignore-next-line unused-export
 export function __resetDeParallelRouterTrialStateForTests(): void {
   deParallelRouterTrialManagedByUs = false;
   deParallelRouterTrialFiredThisProcess = false;
@@ -1429,6 +1428,7 @@ function trackRenderMetrics(
     deParallelRouter: perf?.drawElement?.parallelRouter,
     dePreRouterWorkers: perf?.drawElement?.preRouterWorkers,
     deGateReason: perf?.drawElement?.gateReason,
+    gpuRenderer: perf?.drawElement?.gpuRenderer,
     deWorkerEncode: perf?.drawElement?.workerEncode,
     deVerifyArmed: perf?.drawElement?.verifyArmed,
     deVerifyChecked: perf?.drawElement?.verifyChecked,