Share unavailable() so the Windows sensor logs unavailable transitions

internal/evidence/unavailable.go

@@ -0,0 +1,10 @@
+package evidence
+
+import "log"
+
+// unavailable builds an Unavailable snapshot and logs the reason. It is shared
+// by every platform sensor so an unobservable window is recorded consistently.
+func unavailable(reason string) WindowSnapshot {
+	log.Printf("evidence: %s", reason)
+	return WindowSnapshot{Health: EvidenceHealth{Available: false, Reason: reason}}
+}

internal/evidence/windows.go

@@ -31,7 +31,7 @@ func (windowsSource) Watch(ctx context.Context, onChange func(WindowSnapshot)) {
 			return
 		}
 		if !ok {
-			onChange(WindowSnapshot{Health: EvidenceHealth{Available: false, Reason: "no foreground window"}})
+			onChange(unavailable("no foreground window"))
 			return
 		}
 		onChange(WindowSnapshot{Title: title, Class: class, Health: EvidenceHealth{Available: true}})

internal/evidence/x11.go

@@ -4,7 +4,6 @@ package evidence
 
 import (
 	"context"
-	"log"
 
 	"github.com/jezek/xgb/xproto"
 	"github.com/jezek/xgbutil"
@@ -88,7 +87,3 @@ func snapshot(X *xgbutil.XUtil) WindowSnapshot {
 	}
 }
 
-func unavailable(reason string) WindowSnapshot {
-	log.Printf("evidence: %s", reason)
-	return WindowSnapshot{Health: EvidenceHealth{Available: false, Reason: reason}}
-}