vgsp: fail4 r234 - A-TRACE end-to-end 64KB copy trace + RDW rec-dump arming line

r233: the probe ran (attempt-1 completes now) with the same deterministic
foreign readback, while REC-DUMP/READ-DIVERGE-WIT/READ-ORDER-WIT/ledger
DIVERGE were all absent from the capture. The r231/r233 rings only cover
the transformer_mt window (6-7 GRID-WITs, 15 sema-bigcopy lines, all of
the transformer); the probe's launches are outside the saved ring, so the
witness absence is not yet attributable to the code. Two additions make
the next capture self-contained:

- RDW nrecs=<n> launch_va=<push>: one arming line per forwarded launch
  (budget 256) - a capture can never confuse 'witness did not run' with
  'no recs'; probe-class launches must show nrecs>0.

- A-TRACE, four labeled points for every 64 KB copy and every small
  launch (budgets 128/128):
    pt=P1  H2D source read (src_int4 as ints; expect 0 1 2 3)
    pt=P2  H2D destination right after the copy (dst_int4_after)
    pt=P3  engine-read point: for <=64-rec launches, the first recs'
           source-page content the copy-in stages (w0..15 per rec)
    pt=P4  D2H source read (the engine-authored page as ints)
    pt=P4R D2H host-side readback after the copy
  The probe A buffer is ints 0..16383; the first point where the pattern
  breaks is the bug site.

Stats check for the elision class: r231's probe-window stats show
copy_skipped=0 copy_soft=0 copy_fail=0 and no device-dst guard lines, so
no forwarded/skip elision is in play in that window; the trace decides
where the read/write split actually occurs.

Build green.

(cherry picked from commit 98bfc75410b214f7de3dfc6ef80bff76118ff14d)

0 files changed, 0 insertions, 0 deletions