PINK: async submit + process_intent hot path; async/race flaw audit (pass 5)

N2/N3/N4 (3x Critical async bugs):
- BingxVenueAdapter.submit_async(): awaits backend.submit_intent() directly
  in caller's event loop — no thread-pool, no asyncio.run(), no _backend_snapshot()
- ExecutionKernel.process_intent_async(): same FSM guard logic as sync version;
  replaces venue.submit() with await venue.submit_async(); sync process_intent()
  untouched so all 122 tests stay green
- pink_direct.step() line 952: process_intent() -> await process_intent_async()

restore_state JSON parse (test fix):
- ExecutionKernel.restore_state() wraps Rust FFI in try/except JSONDecodeError
  returns False; matches documented contract; test_restore_corrupt_json_rejected passes

FLAWS doc: pass 5 table added; 21 total fixed; Z6/N5 marked resolved

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

prod/clean_arch/runtime/pink_direct.py

@@ -833,7 +833,7 @@ class PinkDirectRuntime:
         1. Update market state
         2. Decide (policy layer)
         3. Plan (intent layer)
-        4. Translate to KernelIntent -> kernel.process_intent()
+        4. Translate to KernelIntent -> kernel.process_intent_async()
         5. Read final slot + account state from kernel
         6. Persist
         """
@@ -949,7 +949,7 @@ class PinkDirectRuntime:
                 # overshoot an open position.
                 kernel_intent = self._exit_intent_from_slot(kernel_intent)
 
-            outcome = self.kernel.process_intent(kernel_intent)
+            outcome = await self.kernel.process_intent_async(kernel_intent)
 
             # Locate the source of any non-finite intent the kernel rejected:
             # log the full upstream provenance (snapshot price, account capital,