jspi: migration phases 0-7 — build knob, scheduler shim, test successor suite

Toolchain: emsdk 6.0.6 (versions.sh; cache-hash keys on it). Build knob
PCBJAM_ASYNC_BACKEND=jspi|asyncify: build-kicad-target.sh links editors with
-sJSPI + -sJSPI_EXPORTS=@scripts/common/jspi-exports.txt + --pre-js
jspi-scheduler.js (no DYNCALLS, no post-link asyncify pipeline); wx build
stamps the backend and forces clean on flip or unknown provenance;
docker/build.sh passes the knob, seeds the emscripten ports cache from the
volume every launch, jspi postprocess = patch-env-shim only.

scripts/common/shims/jspi-scheduler.js: the JSPI successor scheduler —
token-wait registry, resume turnstile (one armed resume between engine
re-entries, SP swaps only at microtask boundaries), green-region spill
stacks (16-aligned tops), S1 embind mutator FIFO lane + parker wraps, S6
shutdown, libctx integration hooks (suspend/end/quarantine + g_current
arm/clear), SuspendError attributor, lost-wake + stuck-window watchdogs,
__wxWaitDump observability.

Embind: PARKER registrations get emscripten::async() under PCBJAM_JSPI
(wasm/bindings/pcbjam_async_policy.h). nanosleep yields route via the shim.

Tests: tests/asyncify -> tests/jspi successor suite (jspi-stack red/green
shadow-stack battery, jspi-coroutine MiniCoro harness, suspend-races
semantic scenarios + __wxWaitDump books coherence); projects jspi-firefox/
jspi-chrome (asyncify-webkit retired — no JSPI in WebKit); unconditional
Firefox JSPI pref; guard-beacons -> wait-beacons (+wxScheduler/libctxJspi
families); Makefile.wasm links test apps against JSPI with the shim as a
tracked link prerequisite.

Web: WasmTool setRo await + __wxWaitDump forensics, open-flow contained
promise, scheduler-shim.test.ts retargeted (8 green).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NDeBaKKhQztd8KiVtHuyXr

tests/playwright-web.config.ts

@@ -53,15 +53,31 @@ const CHROMIUM_CI_ARGS = process.env.CI
     }
   : {};
 
-// Headless Firefox can't create a GL context on GPU-less CI VMs — run headed
-// under Xvfb (the CI step wraps in xvfb-run) with the no-GPU blocklist bypassed,
-// same as the kicad-firefox project in playwright.config.ts.
+// Firefox prefs. JSPI is default-on only in Firefox >=153; the bundled 144
+// needs the pref — set it UNCONDITIONALLY, exactly like FIREFOX_PREFS_ALWAYS
+// in playwright.config.ts (a CI-gated blob would leave local runs without it).
+// CI additionally runs headed under Xvfb (the CI step wraps in xvfb-run) with
+// the no-GPU blocklist bypassed, since headless Firefox can't create a GL
+// context on GPU-less CI VMs. NOTE: spreads REPLACE launchOptions wholesale —
+// keep this a single composed object, never two competing spreads.
+const FIREFOX_PREFS_ALWAYS = {
+  'javascript.options.wasm_js_promise_integration': true,
+};
 const FIREFOX_CI_OPTS = process.env.CI
   ? {
       headless: false,
-      launchOptions: { firefoxUserPrefs: { 'webgl.force-enabled': true } },
+      launchOptions: {
+        firefoxUserPrefs: {
+          ...FIREFOX_PREFS_ALWAYS,
+          'webgl.force-enabled': true,
+        },
+      },
     }
-  : {};
+  : {
+      launchOptions: {
+        firefoxUserPrefs: { ...FIREFOX_PREFS_ALWAYS },
+      },
+    };
 
 export default defineConfig({
   globalSetup: './web/global-setup-web.ts',