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/audit-061-sub821C4EB0-branch-diff/branch-pcs.txt

@@ -0,0 +1,20 @@
+# AUDIT-061 — conditional branches in sub_821C4EB0 [+0x44, +0xE0] = [0x821C4EF4, 0x821C4F90]
+# Format: PC <tab> mnemonic <tab> target <tab> annotation
+#
+# Range covers PCs from 0x821C4EF4 (cmplwi setting cr6 for branch B1) through
+# 0x821C4F90 (final bgt cr6 of the cmplwi r11,3 jump-table guard).
+#
+# B0 entry probe (function entry) — for sanity-check call counting.
+0x821C4EB0	entry	-	function entry — count calls to sub_821C4EB0
+#
+# Conditional branches:
+0x821C4EF8	beq cr6	0x821C4F20	after cmplwi cr6, r3, 0  (r3 = sub_82150EF8 return).
+0x821C4F3C	bne cr6	0x821C4F7C	after lbz r10, 12932(0x828F<<16)+cmplwi r10,0 — byte test of static flag.
+0x821C4F70	beq cr6	0x821C4F78	after lwz r3, 92(r30) — skip bl 0x824AA3E0 when *(r30+92)==0.
+0x821C4F90	bgt cr6	0x821C5000	after cmplwi cr6, r11, 3 — guards 4-entry jump table at 0x821C4F94..0x821C4FAC.
+#
+# Post-bl PCs we want to count too (taken-paths to sub_821CEDF8 etc.):
+0x821C4F14	bl	0x821CC3F8	call to sub_821CC3F8 (the canary-only 5x callee per AUDIT-056? — actually sub_821CEDF8 is the one, this is sub_821CC3F8). Will instrument to count.
+0x821C4F2C	bl	0x82187C30	call to sub_82187C30 — AUDIT-056 caller-LR.
+0x821C4F60	bl	0x82172370	call to sub_82172370 — significant downstream caller.
+0x821C4F74	bl	0x824AA3E0	call to sub_824AA3E0 — KE/ wait-related?  Conditional on prior beq.