[Audit] round 24: signal-path probes (XEvent::Set + IO + NtDuplicateObject)

Adds AUDIT-HLC probes for every path that signals an XEvent or duplicates
its handle, so the round-23 puzzle (waits completing without visible
NtSetEvent/KeSetEvent) can be cross-referenced by underlying X_KEVENT VA
and by primary handle.

  * NtCreateEvent_inner: always log kevent_va for handle/VA cross-ref
  * XEvent::Set: universal hook prints primary handle + kevent_va + LR;
    catches all paths into the event regardless of shim used
  * NtSetEvent: extended with PPC back-chain walk for caller's guest_lr
    (same idiom as the wait probe), so the signaler function is
    immediately identifiable
  * NtReadFile / NtReadFileScatter / NtWriteFile: log when signal_event
    path fires ev->Set() inline at IO completion (bypasses both
    NtSetEvent and KeSetEvent shims)
  * CompleteOverlappedEx (kernel_state.cc): log when overlapped event
    is signaled at completion
  * NtDuplicateObject: log src/dst handle pair (round-24 confirmed silph
    event is dup'd before signaling, explaining the handle-mismatch
    puzzle between NtSetEvent's `handle=` argument and XEvent::Set's
    primary handle())

Result: silph wait at sub_821CB030+0x1B0 on handle F80000A0 is signaled
via NtSetEvent on handle F80000A8 (the duplicate created by sub_8245D9D8
at lr=0x82450DF4 inside the worker chain sub_82450A28 ← 0xA68 ← 0xB68).
Verdict A confirmed: signaler exists and is reachable, but round-17.β
missed it because the search keyed on the wrong handle. No bypass path;
the worker chain is identical between canary and ours-impl, but ours
signals different handles (work-item queue divergence at sub_82452DC0).

Audit-only diagnostic. No semantic changes. Net delta +86 LOC across 7
files. All probes gated on the existing audit_handle_lifecycle cvar
(default off). Tested via Sylpheed boot (35 s, 4 MB log). Audit-handle-
lifecycle-probes branch, local-only.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/xenia/kernel/xevent.cc

@@ -11,6 +11,8 @@
 
 #include "xenia/base/byte_stream.h"
 #include "xenia/base/logging.h"
+#include "xenia/cpu/thread_state.h"
+#include "xenia/kernel/kernel_flags.h"
 
 namespace xe {
 namespace kernel {
@@ -58,6 +60,13 @@ void XEvent::InitializeNative(void* native_ptr, X_DISPATCH_HEADER* header) {
 }
 
 int32_t XEvent::Set(uint32_t priority_increment, bool wait) {
+  if (cvars::audit_handle_lifecycle) {
+    auto* ts = cpu::ThreadState::Get();
+    uint32_t lr = ts ? static_cast<uint32_t>(ts->context()->lr) : 0u;
+    XELOGKERNEL(
+        "AUDIT-HLC XEvent::Set handle={:08X} kevent_va={:08X} prio={} lr={:08X}",
+        handle(), guest_object(), priority_increment, lr);
+  }
   set_priority_increment(priority_increment);
   event_->Set();
   return 1;