Adds `walk_guest_back_chain` (PPC EABI back-chain walker) and a
`record_create_with_stack` audit hook gated on `--trace-handles-focus`.
NtCreateEvent / NtCreateSemaphore / NtCreateTimer / XamTaskSchedule now
route through the new helper so focused handles capture up to 6 stack
frames at allocation time. Diagnostic-only, read-only memory access:
unfocused handles pay one HashSet lookup, focused ones pay six
back-chain dereferences. Lockstep determinism preserved.
End-to-end finding: handles 0x1004 (8-instance pool via static ctor at
0x8280F810), 0x100c (singleton built inside main()), 0x15e0 (singleton
in distinct cluster) are silph-framework dispatcher objects whose
producer code is unreached at -n 500M. The producer hunt now has class
ownership; vtable/RTTI readout is the next step.
Tests: 576 → 581 green. `--stable-digest -n 100M` instructions=100000002
unchanged. Master HEAD prior: 9d45efe.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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