fix(asyncify): layer 3 — serialize root re-entry out of sleep-wake windows + flight recorder

v0.1.22 still trapped with BOTH guards silent: the fatal rewind's target is
the ROOT context, which layer 2 exempted. All four prod stacks are the same
collision — a fiber completes its yield-back to main while main's sleep-wake
rewind is still on the stack (maybeStopUnwind → trampoline →
finishContextSwitch → doRewind(root) → unreachable), two "resume main" paths
interleaved in one tick; the 8ms-earlier "index out of bounds" is the wake
side of the same event.

Root entry is legal and constant in healthy flow; only the wake-window
overlap is fatal. So: serialize, don't refuse. The shim marks the
synchronous wake window (Asyncify.__inSleepWake around wakeUp) and DEFERS a
root finishContextSwitch landing inside it by one macrotask
([wx-asyncify] root-entry-deferred beacon, trampoline retry) — an ordering
change only, nothing dropped. Suspension recording happens before the
deferral branch, so the yielding fiber's validity survives the wake chain
nulling currData.

Plus a flight recorder: a 96-entry ring of asyncify/fiber events (sleeps,
wakes, every context switch with ROOT/wake-depth, refusals, deferrals),
silent in normal operation, auto-dumped with full machine state next to the
first trap signature in the console; window.__wxAsyncifyDump() on demand.
The next prod export reads like a black box, not a stack-shape puzzle.

.ci-cache-epoch 3→4 (wasm cache key omits scripts/**).

Local: fiber-resume-park 2/2 (one refusal beacon), timer-park 1/1, sweep 20
passed, web fatal+follow 2/2.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_019SE4o46Lnq3hF574FFq8x4

.ci-cache-epoch

@@ -1 +1 @@
-3
+4