Skip compositor tests without recording a failure

Two problems made a missing Wayland compositor look like broken tests.

The cleanup traps ended on a bare conditional, so when a test skipped
before creating its TMPDIR the trap's last command returned 1 and, under
set -e, that overrode the explicit exit 0.

Six tests that launch quickshell had no compositor guard at all, so they
ran anyway and failed on the Qt platform plugin.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

test/shell.d/pointer-move-gate-test.sh

@@ -51,6 +51,11 @@ assert(
 )
 JS
 
+if [[ -z ${WAYLAND_DISPLAY:-} ]]; then
+  pass "no Wayland compositor; skipping pointer movement gate runtime test"
+  exit 0
+fi
+
 if ! command -v quickshell >/dev/null 2>&1; then
   pass "quickshell not installed; skipping pointer movement gate runtime test"
   exit 0