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/kicad/utils/wait-beacons.ts

@@ -1,5 +1,5 @@
-// Guard-beacon extraction for the mailbox/scheduler migration
-// (docs/features/async/17-mailbox-scheduler-plan.md, step S0.3).
+// Wait-beacon extraction (JSPI-era successor of guard-beacons.ts; the
+// mailbox/scheduler migration doc is docs/features/async/17, step S0.3).
 //
 // Every legacy anti-collision guard announces itself on the console when it fires.
 // During the migration each superseded guard is kept as a TRIPWIRE: the mailbox is
@@ -30,6 +30,10 @@ export interface GuardBeaconCounts {
   libcontext: BeaconFamilyCount;
   // open-settle gate giving up (open-flow.ts)
   openSettleFailed: BeaconFamilyCount;
+  // jspi-scheduler.js turnstile/containment beacons (JSPI builds)
+  wxScheduler: BeaconFamilyCount;
+  // libcontext JSPI backend ghost/refused-transition census
+  libctxJspi: BeaconFamilyCount;
   // scheduler build marker — identifies the dual-glue variant, not a guard
   schedulerBuild: boolean;
 }
@@ -45,6 +49,10 @@ const FAMILY_PATTERNS: Record<
   libcontext:
     /\[collab-fcontext\] (jump-refused|jump-refused-hot-main|hot-main-swap-out|jump-hot-into-main|jump-ghost|entry-orphaned)/,
   openSettleFailed: /\[open\] load chain never settled/,
+  // JSPI-era families (jspi-scheduler.js + libcontext's JSPI backend):
+  wxScheduler:
+    /\[wx-scheduler\] (force-clearing stuck window|mailbox tick error|untracked promising entry|activation stack imbalance|resume window misnested)/,
+  libctxJspi: /\[libctx-jspi\] ghost\/refused/,
 };
 
 const OCCURRENCE_RE = /\(occurrence (\d+)\)/;
@@ -61,6 +69,8 @@ export function countGuardBeacons(consoleLines: string[]): GuardBeaconCounts {
     wxAsyncify: emptyFamily(),
     libcontext: emptyFamily(),
     openSettleFailed: emptyFamily(),
+    wxScheduler: emptyFamily(),
+    libctxJspi: emptyFamily(),
     schedulerBuild: false,
   };