Fix: Never pair exclusionMode with exclusiveZone

Quickshell's exclusiveZone setter flips exclusionMode back to Normal as a
side effect, so a window declaring both is at the mercy of which property
the QML engine applies last. The 2026-09-14 Qt update changed that order
and every full-screen overlay slid under the bar.

Each overlay now declares ExclusionMode.Ignore alone. The capture picker
was the visible failure: it started under the bar, the full-output freeze
frame was squeezed into a shorter box, and every selection landed one
bar-height off in the real capture.

tests/quickshell/exclusion-idiom-contract fails any file that pairs them.

tests/quickshell/exclusion-idiom-contract

@@ -0,0 +1,45 @@
+#!/usr/bin/env bash
+
+# A window that wants the whole output must ask for ExclusionMode.Ignore and
+# nothing else. Quickshell's exclusiveZone setter forces exclusionMode back to
+# Normal as a side effect, so a window declaring both
+#
+#     exclusiveZone: 0
+#     exclusionMode: ExclusionMode.Ignore
+#
+# ends up with whichever property the QML engine applied last, and that order
+# is not ours to control: the 2026-09-14 Qt/Quickshell update flipped it, every
+# full-screen overlay slid down under the bar, and the screenshot picker's
+# frozen frame stopped lining up with the screen it was a picture of. This pins
+# the order-independent idiom: Ignore alone, never paired with exclusiveZone.
+
+set -uo pipefail
+
+repo_dir="$(cd "$(dirname "${BASH_SOURCE[0]}")/../.." && pwd)"
+qs="$repo_dir/config/dot/quickshell"
+
+fail() { printf 'exclusion idiom contract: %s\n' "$1" >&2; exit 1; }
+[[ -d "$qs/modules" ]] || fail "missing $qs/modules"
+
+python3 - "$qs" <<'PY'
+import re, sys, pathlib
+qs = pathlib.Path(sys.argv[1])
+problems = []
+ignore = re.compile(r'\bexclusionMode\s*:\s*ExclusionMode\.Ignore\b')
+zone = re.compile(r'^\s*(?:WlrLayershell\.)?exclusiveZone\s*:', re.M)
+checked = 0
+for path in sorted(qs.rglob('*.qml')):
+    text = path.read_text()
+    if not ignore.search(text):
+        continue
+    checked += 1
+    for m in zone.finditer(text):
+        line = text.count('\n', 0, m.start()) + 1
+        problems.append(f"{path.relative_to(qs)}:{line}: exclusiveZone set in a file that uses "
+                        "ExclusionMode.Ignore; drop it, Ignore already means -1")
+if checked == 0:
+    problems.append("no window uses ExclusionMode.Ignore; the overlays this pins are gone")
+if problems:
+    print('\n'.join(problems), file=sys.stderr)
+    sys.exit(1)
+PY