fix: honour the freedesktop expire_timeout direction

The spec says -1 means the server decides and 0 means never; the code had
them swapped, so a plain notify-send (libnotify's default is -1) became
immortal and an explicit never (-t 0) got the urgency default. Found by the
live handover test, where notify-send produced expires 0.

The urgency default is unchanged: low and normal 10s, critical never.

2 files changed, 14 insertions, 10 deletions

diff --git a/internal/notify/policy.go b/internal/notify/policy.go
index c1dc647..5c70390 100644
--- a/internal/notify/policy.go
+++ b/internal/notify/policy.go
@@ -22,8 +22,9 @@ const (
 	Critical Urgency = "critical"
 )
 
-// DefaultTimeoutMS is the balloon lifetime for an urgency when the client sends
-// expire_timeout 0. Critical never expires, which is 0 here.
+// DefaultTimeoutMS is the balloon lifetime for an urgency when the client
+// leaves the choice to the server (expire_timeout -1). Critical never expires,
+// which is 0 here.
 func DefaultTimeoutMS(u Urgency) int64 {
 	switch u {
 	case Low, Normal:
@@ -33,14 +34,17 @@ func DefaultTimeoutMS(u Urgency) int64 {
 	}
 }
 
-// EffectiveTimeoutMS resolves the client's expire_timeout: 0 means the urgency
-// default, -1 means never, anything positive is milliseconds and wins.
+// EffectiveTimeoutMS resolves the client's expire_timeout per the freedesktop
+// spec: -1 means the server decides (the urgency default), 0 means never, and
+// anything positive is milliseconds and wins. The spec is precise about the
+// direction and libnotify's default is -1, so getting it backwards would make
+// every plain notify-send immortal.
 func EffectiveTimeoutMS(expire int32, u Urgency) int64 {
 	switch {
 	case expire == -1:
-		return 0
-	case expire == 0:
 		return DefaultTimeoutMS(u)
+	case expire == 0:
+		return 0
 	default:
 		return int64(expire)
 	}
diff --git a/internal/notify/policy_test.go b/internal/notify/policy_test.go
index ef5bb72..378c573 100644
--- a/internal/notify/policy_test.go
+++ b/internal/notify/policy_test.go
@@ -46,10 +46,10 @@ func TestEffectiveTimeoutMS(t *testing.T) {
 		u      Urgency
 		want   int64
 	}{
-		{"zero uses low default", 0, Low, 10_000},
-		{"zero uses normal default", 0, Normal, 10_000},
-		{"zero critical never", 0, Critical, 0},
-		{"minus one never", -1, Normal, 0},
+		{"minus one uses low default", -1, Low, 10_000},
+		{"minus one uses normal default", -1, Normal, 10_000},
+		{"minus one critical never", -1, Critical, 0},
+		{"zero never", 0, Normal, 0},
 		{"explicit wins", 3_000, Normal, 3_000},
 		{"sub second exact", 1, Normal, 1},
 	}