fix(scripts): capture check/shard rc before watchdog teardown in no-timeout fallback (#2864)

On machines with neither gtimeout nor timeout on PATH, run-verify-parallel.sh
and run-unit-parallel.sh fall back to a bg-pid + sleep-watchdog cap. Both
read $? only after tearing the watchdog down (kill + wait on cap_pid), so the
sentinel .exit files recorded the killed watchdog's status — 143 — instead of
the check/shard's own exit code. Every run reported total failure (verify:
pass=0 fail=31; unit: rc=143 per shard) while every per-check/shard log
showed success.

Capture rc immediately after `wait $pid` in both scripts, and reap the
watchdog's sleep child (pkill -P, children-first — the same orphan quirk the
heartbeat cleanup documents) so the fallback stops leaking one sleep per
check/shard.

Regression tests force the fallback branch hermetically on any host via a
curated PATH with no timeout binaries: the verify dispatcher runs from a
tempdir copy with a stubbed `bun`, pinning exit 0 + all-zero sentinels when
checks pass and the check's own rc (not 143) when one fails; the unit wrapper
runs real two-shard fixture passes, pinning rc=0 sentinels and a real
failure's rc=1.

Co-authored-by: YMYD <53603073+OJ-OnJourney@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

scripts/run-unit-parallel.sh

@@ -133,6 +133,7 @@ for i in $(seq 1 "$N"); do
         env SHARD="$i/$N" \
         bash scripts/run-unit-shard.sh --max-concurrency="$INTRA_CONC" \
         > "$SHARD_LOG" 2>&1
+      rc=$?
     else
       env SHARD="$i/$N" \
         bash scripts/run-unit-shard.sh --max-concurrency="$INTRA_CONC" \
@@ -142,10 +143,20 @@ for i in $(seq 1 "$N"); do
         sleep 5 && kill -KILL "$pid" 2>/dev/null ) &
       cap_pid=$!
       wait "$pid" 2>/dev/null
+      # Capture the shard's exit code from ITS `wait`, before any watchdog
+      # teardown runs. The teardown commands below overwrite $? — the killed
+      # watchdog reports 143 — which used to get stamped into every shard's
+      # sentinel on machines with no gtimeout/timeout: every run "failed"
+      # with rc=143 summaries even when all tests passed.
+      rc=$?
+      # Reap the watchdog's `sleep` child too (pkill -P), then the watchdog.
+      # Killing only the subshell leaves the sleep orphaned until
+      # $SHARD_TIMEOUT elapses — same quirk the heartbeat cleanup below works
+      # around; CI's orphan-process sweep flags those.
+      pkill -P "$cap_pid" 2>/dev/null
       kill "$cap_pid" 2>/dev/null
       wait "$cap_pid" 2>/dev/null
     fi
-    rc=$?
     echo "$rc" > "$LOG_DIR/shard-$i.exit"
     [ "$rc" = "124" ] && echo "WEDGED" > "$LOG_DIR/shard-$i.wedged"
   ) &

scripts/run-verify-parallel.sh

@@ -126,6 +126,7 @@ for c in "${CHECKS[@]}"; do
   (
     if [ -n "$TIMEOUT_BIN" ]; then
       "$TIMEOUT_BIN" "${TIMEOUT}s" bun run "$c" > "$LOG_FILE" 2>&1
+      rc=$?
     else
       bun run "$c" > "$LOG_FILE" 2>&1 &
       pid=$!
@@ -133,10 +134,20 @@ for c in "${CHECKS[@]}"; do
         sleep 5 && kill -KILL "$pid" 2>/dev/null ) &
       cap_pid=$!
       wait "$pid" 2>/dev/null
+      # Capture the check's exit code from ITS `wait`, before any watchdog
+      # teardown runs. The teardown commands below overwrite $? — the killed
+      # watchdog reports 143 — which used to get stamped into every sentinel
+      # on machines with no gtimeout/timeout: verify reported pass=0
+      # fail=<all> while every per-check log said OK.
+      rc=$?
+      # Reap the watchdog's `sleep` child too (pkill -P), then the watchdog.
+      # Killing only the subshell leaves the sleep orphaned until $TIMEOUT
+      # elapses — same quirk the heartbeat cleanup in run-unit-parallel.sh
+      # works around; CI's orphan-process sweep flags those.
+      pkill -P "$cap_pid" 2>/dev/null
       kill "$cap_pid" 2>/dev/null
       wait "$cap_pid" 2>/dev/null
     fi
-    rc=$?
     echo "$rc" > "$EXIT_FILE"
   ) &
   PIDS+=($!)