v1.92.71.0 test(free): end four non-subject waits early and drop a duplicated test block (GSTA-151 D) (#3582)

* test(free): end four non-subject waits early and drop a duplicated test block

setup's _wait_with_deadline polls every 0.1 s on the SECONDS clock; pregate-supervise and gstack-detach wait on pids and go-files instead of fixed sleeps; qa-probe-gates loses its duplicated C2 block; context-identity runs one restore.

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

* test(setup): mark the sub-second wait bound as the contract (gstack-timing-ok)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

* docs(changelog): unreleased entry for the free-suite wait pass (GSTA-151 D)

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

---------

Co-authored-by: capy-ai[bot] <230910855+capy-ai[bot]@users.noreply.github.com>

setup

@@ -1539,15 +1539,15 @@ _kill_tree() {
 # poll the PID and SIGKILL the whole probe tree past the deadline. Returns
 # the probe's exit code, or 124 on timeout.
 _wait_with_deadline() {
-  local pid="$1" deadline_s="$2" waited=0
+  local pid="$1" deadline_s="$2" end
+  end=$((SECONDS + deadline_s))
   while kill -0 "$pid" 2>/dev/null; do
-    if [ "$waited" -ge "$deadline_s" ]; then
+    if [ "$SECONDS" -gt "$end" ]; then
       _kill_tree "$pid"
       wait "$pid" 2>/dev/null || true
       return 124
     fi
-    sleep 1
-    waited=$((waited + 1))
+    sleep 0.1
   done
   wait "$pid"
 }