bench: record device clocks, temperature and power for the whole campaign

A 6-round A/B here reports side noise at the 0.01% level. Clock throttling and
thermal drift move latency by far more than that and leave no trace in
run.log, so the report comes out looking exactly as clean as a run on a stable
machine. The NV run that reproduced PR763 sampled nvidia-smi every 5s
alongside the campaign; the MUSA campaigns had no equivalent, and the parallel
plan makes it worse by heating the whole box.

telemetry.py samples through the backend, so cuda and musa emit the same
columns (index, sm_clock_mhz, mem_clock_mhz, temp_c, power_w, util_pct) and
two machines' campaigns can be read side by side. mthreads-gmi offers no CSV
query mode, so the MUSA path parses --json and strips the units glued onto
each value ("36C", "1888MHz", "477.68W"); its "Power Draw " key carries a
trailing space, matched by stripping rather than by literal.

The device comes from the backend's own visibility variable when not pinned. A
list of devices resolves to no -i at all, sampling every one, rather than
silently picking the first. Dropping the placeholder drops its flag too: a
bare trailing -i fails the sampler instead of widening it.

Telemetry is evidence, not a gate. A missing or unpermitted sampler exits
quietly with its reason in telemetry.err and the campaign runs unchanged.

ab_repeat.sh

@@ -57,6 +57,19 @@ ROOT="runs/ab_repeat_${SWITCH}_$(date +%Y%m%d-%H%M%S)"
 mkdir -p "$ROOT"
 LOG="$ROOT/summary.log"
 STATUS="$ROOT/status.tsv"
+
+# 全程采时钟/温度/功耗。六轮 A/B 声称的是 0.01% 量级的单侧噪声，降频和热漂移
+# 能移动比这大得多的延迟，而且在 run.log 里不留痕迹——报告照样干净。
+# TELEMETRY_INTERVAL=0 关闭。采不到时 telemetry.py 自己安静退出，不影响测试。
+TELEMETRY_INTERVAL="${TELEMETRY_INTERVAL:-5}"
+TELE_PID=""
+if [[ "$TELEMETRY_INTERVAL" != "0" ]]; then
+  python telemetry.py --backend "${ZL_BACKEND:-cuda}" --device "${ZL_DEVICE:-}" \
+    --interval "$TELEMETRY_INTERVAL" --run \
+    > "$ROOT/telemetry.tsv" 2> "$ROOT/telemetry.err" &
+  TELE_PID=$!
+  trap '[[ -n "$TELE_PID" ]] && kill "$TELE_PID" 2>/dev/null' EXIT
+fi
 printf 'round\top\tside\tswitch\trc\telapsed_s\tsuccess\tfailed\treplay_fallback\tno_cudagraph\tcapture_poisoned\n' > "$STATUS"
 
 # 跑一格并逐格登记。事后 grep 也能拿到这些数，但只在有人想起来时才发生；
@@ -157,5 +170,7 @@ sed -i -E $'s/\x1b\\[[0-9;]*[A-Za-z]//g' "$LOG"
 
 echo ">>> 总 log: $(pwd)/$LOG"
 echo ">>> 逐格状态表: $(pwd)/$STATUS"
+[[ -s "$ROOT/telemetry.tsv" ]] && echo ">>> 时钟/温度: $(pwd)/$ROOT/telemetry.tsv"
+[[ -s "$ROOT/telemetry.err" ]] && echo ">>> 遥测提示: $(cat "$ROOT/telemetry.err")"
 echo ">>> 逐算子重出报告: python batch_summary.py --ab-rounds $ROOT/<op> --label <op>"
 echo ">>> 解读要点: 逐轮区间宽说明判定不稳；单侧噪声大说明机器不稳；两者含义不同"