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-c25-mm-allocator-family/re-validation.md

@@ -0,0 +1,63 @@
+# Phase C+25 — Re-validation
+
+## Gates
+
+| # | Gate | Status | Evidence |
+|---|---|---|---|
+| 1 | Build clean | ✅ | `cargo build --release` succeeds; only pre-existing dead-code warning. |
+| 2 | Phase B `image_canonical_sha256` unchanged | ✅ | Zero engine LOC modified → Phase B hash is `ea8d160e…` by construction. |
+| 3 | Engine determinism (3× cold) | ✅ | `c25-digest-rep{1,2,3}.json` all identical: instructions=50000007 imports=40390 unimpl=0 draws=0 swaps=1 unique_render_targets=0. |
+| 4 | Main matched-prefix advances past 105,112 | ✅ | **105,112 → 105,128 (+16)** — see `diff-postfix.md`. |
+| 5 | Sister chains preserved | ✅ | 4→11=11, 7→2=32, 12→7=4, 14→9=41, 15→10=16 — all unchanged vs Phase W. |
+| 6 | Kernel tests pass | ✅ | xenia-kernel: 217 passed, 0 failed (unchanged baseline). |
+| 7 | Diff-tool unit tests pass | ✅ | 39 baseline + 4 new C+25 tests = 43 PASS. |
+| 8 | `--no-canonicalize-allocators` backward-compat | ✅ | Flag unchanged; raw-VA comparison still available. |
+| 9 | Progression metric — **PRIMARY gate** | ⚠️ **NEGATIVE** | swaps=1, draws=0, unique_render_targets=0. **Wedge persists per Phase W finding.** |
+
+## Per-chain matched-prefix delta
+
+| chain | Phase W (pre) | C+25 (post) | Δ |
+|---|---|---|---|
+| canary tid=6 → ours tid=1 (main) | 105,112 | **105,128** | **+16** |
+| canary tid=4 → ours tid=11 | 11 | 11 | 0 |
+| canary tid=7 → ours tid=2 | 32 | 32 | 0 |
+| canary tid=12 → ours tid=7 | 4 | 4 | 0 |
+| canary tid=14 → ours tid=9 | 41 | 41 | 0 |
+| canary tid=15 → ours tid=10 | 16 | 16 | 0 |
+
+Zero regressions on any chain.
+
+## Progression metric (PRIMARY)
+
+3 cold reproducible runs:
+
+| field | rep1 | rep2 | rep3 | vs Phase W |
+|---|---|---|---|---|
+| instructions | 50000007 | 50000007 | 50000007 | unchanged |
+| imports | 40390 | 40390 | 40390 | unchanged |
+| unimpl | 0 | 0 | 0 | unchanged |
+| **draws** | **0** | **0** | **0** | **unchanged** |
+| **swaps** | **1** | **1** | **1** | **unchanged** |
+| **unique_render_targets** | **0** | **0** | **0** | **unchanged** |
+| shader_blobs_live | 0 | 0 | 0 | unchanged |
+| texture_cache_entries | 0 | 0 | 0 | unchanged |
+
+**Verdict: matched-prefix advanced (+16) but the wedge is structurally
+unchanged.** This is the expected outcome per cascade-prediction gate E (~10%
+probability of movement). The C+25 fix is a diff-tool canonicalization, not
+an engine behavior change; the engine's boot trajectory is byte-identical
+to Phase W (digest fields prove it).
+
+The next divergence at idx 105,128 (`thread.create.ctx_ptr`: canary
+`0xbe56bb3c` in vC0… heap region vs ours `0x42453b3c` in unified heap) is
+another deferred-Path-β symptom — a heap-VA leaking into a non-return
+payload field. Canonicalization could be extended to cover specific payload
+fields too, but that's a follow-up scope decision.
+
+## Determinism note
+
+The engine binary is `xrs-c25` (renamed from `xrs-verify-c23`; built from the
+same source tree, which is unchanged by C+25 since the C+25 diff is
+Python-only). All 3 cold runs used `XENIA_CACHE_WIPE=1` and produced
+identical digests, confirming the engine's cold-boot trajectory is the same
+as Phase W's `73e99d6002…`-class run.