fix(arrange): stop dimming unfocused windows — it read as a blur change

Unfocused windows were placed at 0.90 opacity (0.85 for overlays). On the
DE's translucent backplate that does not look like dimming: it thins the
plate's tint, so the blurred backdrop shows through with more contrast and
the window looks less frosted than the focused one. Every focus click then
appeared to ADD blur to the clicked window, though the blur radius never
changed. Measured in a headless shadow session: the focused plate's
interior was 0.62 * unfocused + 43 (grey levels); with both levels at 1.0
the two states differ by 0.2.

Both constants are now 1.0. The knob and `opacity_enabled` stay, so the
level can be re-tuned without re-plumbing; the policy test covers the
pass-through with a literal level instead of the DE constants.

Co-Authored-By: Claude Fable 5.1 <[email protected]>
Claude-Session: https://claude.ai/code/session_0183SazyM4GDN4jHRbkEYV53

 src/arrange.rs | 24 ++++++++++++++++++------
 1 file changed, 18 insertions(+), 6 deletions(-)

diff --git a/src/arrange.rs b/src/arrange.rs
index 8c01564..33cd147 100644
--- a/src/arrange.rs
+++ b/src/arrange.rs
@@ -198,8 +198,16 @@ const OVERLAY_DEC_H: i32 = 16;
 /// Windows further than this many pixels outside the output are culled.
 const OFFSCREEN_MARGIN: f64 = 50.0;
 
-pub const OVERLAY_UNFOCUSED_OPACITY: f32 = 0.85;
-pub const NORMAL_UNFOCUSED_OPACITY: f32 = 0.90;
+/// Opacity of an unfocused window's scene tree. Both are 1.0 — the same as
+/// focused — since 2026-09-03. They used to be 0.85 (overlay) and 0.90
+/// (normal), and on a translucent backplate that dimming did not read as
+/// "dimmer": it thinned the plate's tint, so the blurred backdrop showed
+/// through with more contrast and the window looked LESS frosted than the
+/// focused one, which then appeared to gain blur on every focus click. The
+/// blur radius never changed. Keep the knob (and `opacity_enabled`) so the
+/// level can be re-tuned without re-plumbing.
+pub const OVERLAY_UNFOCUSED_OPACITY: f32 = 1.0;
+pub const NORMAL_UNFOCUSED_OPACITY: f32 = 1.0;
 
 pub fn window_opacity(is_focused: bool, opacity_enabled: bool, unfocused: f32) -> f32 {
     if is_focused || !opacity_enabled { 1.0 } else { unfocused }
@@ -1834,10 +1842,14 @@ mod tests {
 
     #[test]
     fn opacity_policy() {
-        assert_eq!(window_opacity(true, true, OVERLAY_UNFOCUSED_OPACITY), 1.0);
-        assert_eq!(window_opacity(false, false, OVERLAY_UNFOCUSED_OPACITY), 1.0);
-        assert_eq!(window_opacity(false, true, OVERLAY_UNFOCUSED_OPACITY), 0.85);
-        assert_eq!(window_opacity(false, true, NORMAL_UNFOCUSED_OPACITY), 0.90);
+        // Focused, or dimming disabled: always fully opaque.
+        assert_eq!(window_opacity(true, true, 0.5), 1.0);
+        assert_eq!(window_opacity(false, false, 0.5), 1.0);
+        // Unfocused with dimming enabled: the given level passes through.
+        assert_eq!(window_opacity(false, true, 0.5), 0.5);
+        // The DE levels: an unfocused window looks exactly like a focused one.
+        assert_eq!(window_opacity(false, true, OVERLAY_UNFOCUSED_OPACITY), 1.0);
+        assert_eq!(window_opacity(false, true, NORMAL_UNFOCUSED_OPACITY), 1.0);
     }
 
     fn snap(app_id: &str) -> WindowSnapshot {