fix: preserve GPUI lifetime and avoid WASAPI silence warnings

scripts/validate/linux-background.sh

@@ -81,6 +81,34 @@ swaymsg '[app_id="dev.clipbin.Clipbin"] kill' >/dev/null
 wait_windows 0
 menu 1
 wait_windows 1
+# Repeated reopen must release each UI's threads and allocation state.
+measure() {
+    python3 - "${app}" "$1" <<'PYMETRICS'
+import pathlib,sys
+status=dict(line.split(':',1) for line in pathlib.Path(f'/proc/{sys.argv[1]}/status').read_text().splitlines() if ':' in line)
+print(f"{sys.argv[2]}\t{status['Threads'].strip()}\t{status['VmRSS'].split()[0]}")
+PYMETRICS
+}
+measure 0 > "${out}/reopen-metrics.tsv"
+for cycle in $(seq 5); do
+    swaymsg '[app_id="dev.clipbin.Clipbin"] kill' >/dev/null
+    wait_windows 0
+    sleep 1
+    menu 1
+    wait_windows 1
+    sleep 1
+    measure "${cycle}" >> "${out}/reopen-metrics.tsv"
+done
+cat "${out}/reopen-metrics.tsv"
+python3 - "${out}/reopen-metrics.tsv" <<'PYBOUNDS'
+import pathlib,sys
+rows=[tuple(map(int,line.split())) for line in pathlib.Path(sys.argv[1]).read_text().splitlines()]
+assert max(r[1] for r in rows[1:]) <= rows[0][1]+4, rows
+# Allow the first reopen to warm caches; later windows must stay bounded.
+rss=[r[2] for r in rows[1:]]
+assert max(rss)-min(rss) <= 32*1024 and rows[-1][2] <= rows[0][2]+64*1024, rows
+print('PASS five close/reopen cycles have bounded thread count and RSS')
+PYBOUNDS
 # Audio delivery loss must be visible in the application and real tray tooltip.
 kill "$(cat "${CLIPBIN_RIG_DIR}/pulse.pid")"
 for _ in $(seq 15); do grep -q 'recorder_status=Degraded' "${out}/desktop.log" && break; sleep 1; done