fix(ci): serialize the heavy 3D-viewer e2e specs (dedicated chromium-ci-3d project)

The three heavy 3D-viewer specs (3d-viewer, 3d-viewer-deadlock, 3d-viewer-models)
crashed on CI (run 28604015154): "Target crashed", "browser has been closed", and a
black frozen canvas. Each boots the 3D-enabled pcbnew build, which pre-warms
~hardwareConcurrency*2+8 (~68 on the 30-core VM) Web Workers AND runs a multi-threaded
CPU raytracer over SwiftShader software-WebGL. Under fullyParallel the three spec FILES
run in separate browser processes concurrently, and the simultaneous raytrace tabs
exhaust the shared GPU process's ~16 live-WebGL-context limit / renderer memory. The
pool pre-warm (the deadlock fix, 7630c7e) is correct and present in the tested binary;
per-file isolation prevented in-process Worker accumulation but NOT this cross-process
concurrency — the gap these specs' first CI exposure hit.

Fix (test-orchestration only; no wasm/submodule changes):
- Route the three specs to a dedicated `chromium-ci-3d` Playwright project (own
  outputDir=pw-artifacts/kicad-3d so its failure traces survive the later perf run's
  wipe; the existing tests/pw-artifacts/** upload already captures it).
- test:kicad:ci runs it as a SECOND `playwright test` pass with --workers=1, so at most
  one raytrace tab is alive at a time (the environment in which a single 3D load is
  reliably green — docs/features/3d-raytracer/README.md §7). An exit-code-aggregating
  sequencer runs both phases and fails if either fails (no silent skip of the 3D pass).
- Cap phase-1 CI workers to 12 as headroom under the WebGL-context cap.
- Log a resource-diagnostic snapshot (hardwareConcurrency, pthread pool, GL-canvas
  count, wasm/JS heap) before each 3D interaction so any recurrence is attributable.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

tests/playwright-kicad.config.ts

@@ -118,6 +118,24 @@ const BIG_MODULE_SPECS = [
   "**/occ-probe.spec.ts",
 ];
 
+// The heavy 3D-viewer specs each boot the 3D-enabled pcbnew build, which pre-warms
+// ~hardwareConcurrency*2+8 Web Workers AND runs a multi-threaded CPU raytracer over
+// SwiftShader software-WebGL. Under fullyParallel these separate spec FILES land in
+// separate browser processes CONCURRENTLY, and the simultaneous raytrace tabs exhaust
+// Workers / wasm heap / the shared GPU process's ~16 live-WebGL-context limit → the tab
+// crashes ("Target crashed" / "browser has been closed" / a black frozen canvas). Per-file
+// isolation (own worker) prevents in-process Worker accumulation but NOT this cross-process
+// concurrency. They STAY in BIG_MODULE_SPECS (so firefox keeps ignoring them — the ~190 MB
+// module OOMs SpiderMonkey/x86), but on CI they run in the dedicated 'chromium-ci-3d' project,
+// which test:kicad:ci invokes with --workers=1 so at most ONE raytrace tab is alive at a time.
+// (footprint-3d-preview.spec.ts is a placeholder glob — no such file exists yet — harmless.)
+const THREE_D_HEAVY_SPECS = [
+  "**/3d-viewer.spec.ts",
+  "**/3d-viewer-deadlock.spec.ts",
+  "**/3d-viewer-models.spec.ts",
+  "**/footprint-3d-preview.spec.ts",
+];
+
 // Runtime-perf specs run ONLY on the Chromium 'perf' project below: they need
 // CDP CPU throttling (Chromium-only) and pcbnew needs V8. Excluded from the
 // firefox/chromium projects so they don't double-run there.
@@ -137,10 +155,13 @@ export default defineConfig({
   // as playwright.config.ts): the load-pcb post-load clipboard crash that can
   // close the page on Firefox, and the calculator first-run-wizard timing race.
   retries: process.env.CI ? 2 : 1,
-  // Run parallel workers on CI too (Playwright default ≈ 50% of cores), same as
-  // local — the serial CI run was the dominant wall-clock cost. Cap (e.g. '50%'
-  // or a fixed count) if contention OOMs/flakes; retries:2 covers transient.
-  workers: undefined,
+  // Run parallel workers on CI too, same as local — the serial CI run was the dominant
+  // wall-clock cost. Capped to a fixed 12 on CI (down from Playwright's default ≈ 50% of
+  // cores = ~15 on the 30-core VM) as defense-in-depth for the ~16 live-WebGL-context limit
+  // in Chromium's shared GPU process: ~15 GAL-canvas tabs already brush that cap. The heavy
+  // 3D-viewer specs (a *second* WebGL context each) no longer run here — they're isolated to
+  // the serial 'chromium-ci-3d' project — so 12 is only headroom, not the primary fix.
+  workers: process.env.CI ? 12 : undefined,
   reporter: "html",
   timeout: 180000, // KiCad WASM needs more time to load (3 minutes)
 
@@ -210,7 +231,29 @@ export default defineConfig({
       // --enable-unsafe-swiftshader: newer Chromium refuses software WebGL in
       // headless without it.
       name: "chromium-ci",
-      testMatch: BIG_MODULE_SPECS,
+      // Every big-module spec EXCEPT the heavy 3D-viewer ones — those move to the
+      // serial 'chromium-ci-3d' project below so they never raytrace concurrently.
+      testMatch: BIG_MODULE_SPECS.filter((s) => !THREE_D_HEAVY_SPECS.includes(s)),
+      use: {
+        ...devices["Desktop Chrome"],
+        viewport: { width: 1280, height: 720 },
+        launchOptions: {
+          args: ["--enable-unsafe-swiftshader"],
+        },
+      },
+    },
+    {
+      // CI-only serial carrier for the heavy 3D-viewer specs (see THREE_D_HEAVY_SPECS).
+      // Same runtime as chromium-ci; test:kicad:ci invokes this project in a SEPARATE
+      // `playwright test` pass with --workers=1, so at most one raytrace tab is alive at a
+      // time (the environment in which a single 3D load is reliably green — see
+      // docs/features/3d-raytracer/README.md §6-§7). Own outputDir so its start-of-run
+      // cleanup doesn't wipe chromium-ci's retained traces, and so its own failure traces
+      // survive the later `test:perf` run's pw-artifacts/kicad wipe; the CI upload glob
+      // tests/pw-artifacts/** already captures it, so no workflow change is needed.
+      name: "chromium-ci-3d",
+      testMatch: THREE_D_HEAVY_SPECS,
+      outputDir: process.env.CI ? "pw-artifacts/kicad-3d" : "test-results",
       use: {
         ...devices["Desktop Chrome"],
         viewport: { width: 1280, height: 720 },