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/producer/src/services/render/perfSummary.ts

@@ -111,6 +111,9 @@ function aggregateDrawElement(
   const gateReasons = [
     ...new Set(perfs.map((p) => p.deGateReason).filter((r): r is string => !!r)),
   ].sort();
+  const gpuRenderers = [
+    ...new Set(perfs.map((p) => p.gpuRenderer).filter((r): r is string => !!r)),
+  ].sort();
   const drain = de.drainStats;
   return {
     mode: modes.join("|") || "unknown",
@@ -121,6 +124,7 @@ function aggregateDrawElement(
     parallelRouter: de.parallelRouter ?? "none",
     preRouterWorkers: de.preRouterWorkers,
     gateReason: gateReasons.length > 0 ? gateReasons.join("|") : undefined,
+    gpuRenderer: gpuRenderers.length > 0 ? gpuRenderers.join("|") : undefined,
     workerEncode: perfs.some((p) => p.deWorkerEncode),
     verifyArmed: perfs.reduce((sum, p) => sum + (p.deVerifyArmed ?? 0), 0),
     verifyChecked: drain?.verifyChecked ?? 0,

packages/producer/src/services/renderOrchestrator.ts

@@ -498,6 +498,8 @@ export interface RenderPerfSummary {
     preRouterWorkers?: number;
     /** Engine init-time gate: swiftshader | css_effect:* | at_risk_timeline | 3d_init_failed | supersampling | render_mode_hint. */
     gateReason?: string;
+    /** Raw WebGL renderer string from DE session init (ANGLE backend + GPU vendor); |-joined across parallel sessions. */
+    gpuRenderer?: string;
     /** Worker-encode drain (the verified path) was active. */
     workerEncode: boolean;
     /** Self-verification ground-truth samples armed at init. */