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/phase-c23-keWait-timeout-encoding/broad-impact.md

@@ -0,0 +1,61 @@
+# Phase C+23 broad-impact assessment (2026-05-18)
+
+## Resolved
+
+- **D-NEW-2 (C+17 catalog)** — KeWait timeout `wait.begin.timeout_ns`
+  on canary tid=12 → ours tid=7 idx=3. Was 429466729600 (broken
+  positive sign-extension); now -30000000 matching canary exactly.
+  Sister chain advances 3 → 4.
+
+## Advanced
+
+- **`addis` opcode semantics across the entire CPU interpreter**.
+  Any place in any guest binary using `lis`/`addis` with a negative
+  immediate that flows into a 64-bit `std`, `mr`, `orx`, or anything
+  else that propagates the full GPR value will now produce
+  canary-equivalent behavior. The KeWait timeout was just the first
+  observable symptom in Sylpheed's cold-vs-cold trajectory.
+
+## Persisted (no change)
+
+- Main matched-prefix tid=6→1 = **104,607** (the C+22 scheduler-
+  determinism asymmetry is unaffected by this fix).
+- Sister chains tid=4→11 (11), tid=7→2 (32), tid=14→9 (41),
+  tid=15→10 (16).
+- Phase B `image_canonical_sha256 = ea8d160e9369328a5b922258a92113ef
+  b8d7ce3e1a5c12cc521e375985c91c18`.
+- Kernel tests 204 (unchanged — no kernel-side code change).
+
+## NEW
+
+- **D-NEW-2.1 (idx=4 sister chain canary tid=12 → ours tid=7)**:
+  `KeWaitForSingleObject` return value canary=258 (TIMEOUT) vs
+  ours=0 (SUCCESS). Same C+20/C+22 family — scheduler-determinism;
+  ours's monolithic-thread runner allows the wait to return
+  SUCCESS where canary's contended scheduler lets the 30 ms timeout
+  elapse with no signaler. Out of scope for this phase; same
+  parallel scheduler-determinism track recommended in C+22.
+
+- **CPU correctness probe**: opportunity for a low-key audit of
+  every "32-bit ABI defensive truncation" in
+  `xenia-cpu/src/interpreter.rs` for other ops that legitimately
+  need 64-bit sign-extension at the producer rather than truncation.
+  Quick mental scan suggests `addis` was likely the only such case;
+  `addi` already extends via `simm16 as i64 as u64`, `ori`/`oris`
+  are pure 64-bit OR. Not a blocking concern.
+
+## Test count delta
+
+| crate         | pre-C+23 | post-C+23 | delta |
+|---------------|----------|-----------|-------|
+| xenia-cpu     | 288      | 291       | +3    |
+| xenia-kernel  | 204      | 204       | 0     |
+
+## Cold-stable digest delta
+
+| baseline               | pre-C+23                          | post-C+23                         |
+|------------------------|-----------------------------------|-----------------------------------|
+| ours-cold det-fields   | e1dfcb1559f987b35012a7f2dc6d93f5  | 23cf4c4cbf61a577caa4118ab2308ba6  |
+| Phase B image_canonical| ea8d160e9369…                     | ea8d160e9369…  (UNCHANGED)        |
+
+3× ours-cold runs all yield the new digest. Determinism preserved.