handoff: VSync/event-wedge fixes + iterate 2.A–2.BC research notes

Source changes (dormant parity infra, retained from iterate 2.AI/2.AO):
- xenia-kernel/exports.rs: nt_create_event manual_reset polarity +
  related event wiring
- xenia-gpu/mmio_region.rs: D1MODE_VBLANK_VLINE_STATUS hardcode parity

Also lands the audit-runs/ analysis notes (.md/.txt/.json digests) for the
iterate 2.x VSync/0x10e8/0x1004 wedge investigation. Raw trace dumps
(.jsonl/.gz/.csv/.stdout) and agent worktrees (.claude/) are gitignored as
regenerable local artifacts — see memory + HANDOFF for the running findings.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

audit-runs/iterate-2Y-tid14-critsec-lr-trace/findings.json

@@ -0,0 +1,24 @@
+{
+  "iterate": "2.Y",
+  "date": "2026-06-01",
+  "orchestrator_entry_pc": "0x821c4ad0",
+  "orchestrator_tid_this_run": 17,
+  "orchestrator_tid_in_2V": 14,
+  "gap_window_ns": [
+    2000000000,
+    16000000000
+  ],
+  "tid17_imports_in_gap": {
+    "NtWaitForMultipleObjectsEx": 168909,
+    "RtlEnterCriticalSection": 168908,
+    "RtlLeaveCriticalSection": 168908
+  },
+  "tid17_lr_histogram_in_gap": {
+    "0x8245654c (RtlEnterCS LR)": 168908,
+    "0x8245663c (RtlLeaveCS LR)": 168908
+  },
+  "containing_function": "sub_82456530",
+  "outer_loop_function": "sub_82456420",
+  "wait_status_observed": "0x00000001 (handle index 1 signaled, every cycle)",
+  "classification": "design-intended periodic poll with permanently-signaled wake handle (handle[1])"
+}