test(asyncify): red-green race harness + ablation flags, unwind-catch shim, spec tightening, decisions docs

The asyncify single-slot work, executed red-green (full ledger:
docs/features/asyncify-arbiter/redgreen.md; decisions record:
docs/features/async/07-decisions-and-outcome.md):

- tests/apps/standalone/asyncify-races/ + tests/asyncify/ + dedicated
  playwright config: 8 scenarios reproducing the KiCad asyncify failure
  family with the kicad-faithful startup topology (pre-park fiber swap →
  park throw through the live trampoline). Built in 3 variants; the
  SHIM_DISABLE_TRAMPOLINE_HEAL / SHIM_DISABLE_HANDLESLEEP ablation builds
  keep the historical hang and index-out-of-bounds crash reproducible
  forever (mutation-style pins for the existing shims).
- scripts/common/shims/handlesleep.js: catch the "unwind" park sentinel
  in the wakeUp path — when main's last pre-park suspension was a sleep,
  the main-loop park throw escaped through that sleep's promise reaction
  as an uncaught rejection (the calculator/gerbview console errors).
- scripts/common/inject-dyncall-shims.sh: SHIM_DISABLE_* ablation knobs.
- Spec tightening (the acceptance bar): 'uncaught exception: unwind'
  tolerance DELETED from pcbnew/eeschema specs; load-pcb gained a hard
  clean-console gate over 5 asyncify corruption signatures.
- wxwidgets pointer bump: modal LIFO resolvers, pump resolve-on-error,
  sync clipboard IsSupported (014f67e6c1).

Final state: asyncify suite 7/7, wx e2e 291/292 (1 skip), KiCad e2e 40
passed / 2 skipped with ZERO corruption signatures in any log across all
six apps.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/common/shims/handlesleep.js

@@ -52,7 +52,20 @@ if (typeof Asyncify !== "undefined") {
               Asyncify.currData = sleepCtx.capturedData;
             }
             cleanup();
-            return wakeUp(result);
+            try {
+              return wakeUp(result);
+            } catch (e) {
+              // emscripten_set_main_loop(...,1) parks main() by throwing the
+              // "unwind" sentinel. When main's LAST pre-park suspension was a
+              // sleep, main is resumed from THIS wakeUp, so the sentinel
+              // propagates here instead of into callMain's catch — surfacing as
+              // an uncaught "unwind" promise rejection. Swallow it exactly like
+              // callMain/handleException do on the direct path.
+              if (e === "unwind") {
+                return;
+              }
+              throw e;
+            }
           });
         });
       } catch (e) {