fix(engine): bucket gpu_renderer + cover the failure cohort (review)

Three review findings on the win32 drawElement PR:

1. gpu_renderer shipped the raw UNMASKED_RENDERER_WEBGL string — unbounded,
   driver-authored, GPU-model-specific, and |-joined across parallel
   sessions, i.e. high cardinality by construction, against this file's own
   convention of sanitizing engine-sourced strings (deGateReason is a
   bucket; error messages go through redactTelemetryString). Now bucketed at
   the source by classifyGpuRenderer to <backend>/<vendor>
   (metal/apple, d3d11/nvidia, swiftshader/other, ...), which is the whole
   analytic signal the win32 rollout needs and nothing else. The raw string
   never leaves the engine.

2. gpu_renderer reached render_complete only, so a crashed render — the
   cohort the field exists to attribute — carried no backend. It now rides
   RenderCaptureObservability (deGpuRenderer, sourced from the live probe
   session like the de_* counters), so both render_complete and
   render_error carry it and a hard failure still reports its GPU backend.
   On render_complete the perfSummary value still wins by spread order.

3. Restore the fallow-ignore-next-line suppression above
   __resetDeParallelRouterTrialStateForTests: CLI test files are not fallow
   entry points, so removing it fails the CI dead-code audit (local
   pre-commit passed only because of its changed-file scope).

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

packages/engine/src/services/frameCapture.ts

@@ -34,6 +34,7 @@ import {
   shouldDefaultCaptureBeyondViewport,
 } from "./screenshotService.js";
 import {
+  classifyGpuRenderer,
   detectGpuBackend,
   injectDrawElementCanvas,
   captureDrawElementFrame,
@@ -147,10 +148,12 @@ export interface CaptureSession {
   /** True if running on SwiftShader (detected at init). Undefined before init. */
   isSwiftShader?: boolean;
   /**
-   * Raw WebGL UNMASKED_RENDERER_WEBGL string, captured alongside the
-   * SwiftShader probe at DE session init (e.g. "ANGLE (NVIDIA, D3D11 ...)").
-   * Surfaces in CapturePerfSummary → render telemetry so backend-specific
-   * drawElement damage (Metal vs D3D11 vs GL) clusters attributably.
+   * Low-cardinality GPU bucket (`<backend>/<vendor>`, e.g. `d3d11/nvidia`)
+   * derived from the WebGL renderer at DE session init. Surfaces in
+   * CapturePerfSummary → render telemetry so backend-specific drawElement
+   * damage (Metal vs D3D11 vs GL) clusters attributably. The raw
+   * driver-supplied string is deliberately NOT retained — see
+   * classifyGpuRenderer.
    */
   gpuRenderer?: string;
   /** drawElementImage canvas was injected and is ready for capture. */
@@ -713,7 +716,7 @@ async function initDrawElementOrTransparentBackground(
   if (useDrawElement) {
     const gpuBackend = await detectGpuBackend(page);
     session.isSwiftShader = gpuBackend.isSwiftShader;
-    session.gpuRenderer = gpuBackend.renderer ?? undefined;
+    session.gpuRenderer = classifyGpuRenderer(gpuBackend.renderer);
     const transparent = session.options.format === "png";
     async function routeToFallback(): Promise<void> {
       session.captureMode = session.launchCaptureMode;