staging CI green-up: P-1 apply-slot wedge under JSPI, popup P-4 regression, ysync double-seed header, spec fixes

- P-1 (findings-p.spec P-1c red on CI + locally): a JS exception thrown from a
  window.kicadCollab wire callback does NOT reach the C++ catch(...) — under
  JSPI it REJECTS the promising coroutine entry, slot.done never flips and the
  apply slot is busy for the page's life. Three layers: libcontext flags the
  rejected record dead (kicad → d0afbc4bd3),
  drainApplies() reaps a !done && !CanResume() body, and every EM_ASM
  window.kicadCollab.onX(...) call is try/catch-guarded (collab_common.h,
  kicad_editor/eeschema/pl_editor embind).
- popup.spec 'dismisses on outside click': wx P-4 SetFocus delegation excluded
  for wxPopupWindow (wxwidgets → a7436d1052).
- ysync-two-tab concurrent seed: repairLayoutY + seedNonce retraction deleted
  both headers (pcbjam-shared → 8dabf2e).
- dark-mode.spec: stale light-mode reference (pre wx fa46f1822c DOM
  re-projection) replaced with the CI chromium render.
- items-wire-batch-loss.spec: precondition obsolete after P-5 — poisoned entry
  is now synthetic, plus a P-5 contract assertion (field blob == '').
- presence-ghost-peer.spec: skip early when no /parties/ socket (CI web e2e
  runs the BroadcastChannel provider); findings-p1.spec: polled click-select
  precondition.

Local: kicad-chromium findings/presence/ysync/collab 59/59, popup 7/7,
dark-mode 1/1, pcbjam-shared vitest 249/249.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01LvvARNMxQrq17vogn3REMU

tests/web/presence-ghost-peer.spec.ts

@@ -89,6 +89,13 @@ for (const mode of ['half-open', 'unclean-close'] as const) {
     const ctxA = await browser.newContext();
     const ctxB = await browser.newContext();
     const alice = await bootAs(ctxA, 'alice');
+    // Gate BEFORE the roster assertion: on the BroadcastChannel provider (CI's
+    // standalone preview has no apps/sync) two browser CONTEXTS never see each
+    // other, so bob would wait 30s for an alice that cannot arrive.
+    const liveWs = await alice.evaluate(
+      () => (window as unknown as { __wsList: Array<{ ws: WebSocket; url: string }> }).__wsList.filter((w) => w.ws.readyState === 1 && /\/parties\//.test(w.url)).length,
+    );
+    test.skip(liveWs === 0, 'no live websocket on alice — BC stack (no apps/sync), nothing to lose');
     const bob = await bootAs(ctxB, 'bob');
     await openOverlayMenu(bob);
     await expect(bob.locator('[data-presence-user="alice"]')).toBeVisible({ timeout: 30000 });