chore(claude-do): UsageGate: Parallelitaet stufenweise drosseln statt erst bei

## Kontext: Limits sind Fenster, nicht Summen

Die Runs laufen ueber das Claude-Abo. Limits greifen pro 5h-Fenster und pro 7 Tage. Nicht die Wochensumme tut weh, sondern dass ein Agent-Burst ein Fenster leerraeumt, in dem Mika selbst interaktiv arbeiten will.

## Messgrundlage (alle Transcripts unter ~/.claude/projects)

Agent-Runs sind ueber die ganze Historie nur **18,4 %** des Account-Verbrauch

ClaudeDo-Task: 87105f5e-c4f4-4af4-ae60-89cd2e153e3c

src/ClaudeDo.Worker/Usage/UsageSnapshotBuilder.cs

@@ -46,6 +46,17 @@ public sealed class UsageSnapshotBuilder
             .Select(l => new UsageLimitDto(l.Kind, l.Group, l.Percent, l.Severity, l.ResetsAt, l.ScopeModelDisplayName, l.IsActive))
             .ToList();
 
+        var configuredSlots = Math.Max(1, settings.MaxParallelExecutions);
+        var effectiveSlots = snapshot is null || lastError is not null
+            ? configuredSlots
+            : UsageThrottle.EffectiveSlots(
+                configuredSlots, snapshot.FiveHour?.Utilization, snapshot.SevenDay?.Utilization,
+                settings.UsageThrottleSoftPct, settings.UsageThrottleHardPct,
+                settings.UsageGateFiveHourPct, settings.UsageGateSevenDayPct);
+        var throttleBucket = effectiveSlots < configuredSlots
+            ? DecisiveBucket(snapshot?.FiveHour?.Utilization, snapshot?.SevenDay?.Utilization)
+            : null;
+
         return new UsageSnapshotDto(
             snapshot?.FiveHour?.Utilization,
             snapshot?.FiveHour?.ResetsAt,
@@ -58,6 +69,15 @@ public sealed class UsageSnapshotBuilder
             decision.Reason,
             snapshot?.FetchedAtUtc,
             isStale,
-            lastError);
+            lastError,
+            configuredSlots,
+            effectiveSlots,
+            throttleBucket);
+    }
+
+    private static string? DecisiveBucket(double? fiveHourPct, double? sevenDayPct)
+    {
+        if (fiveHourPct is null && sevenDayPct is null) return null;
+        return (fiveHourPct ?? 0) >= (sevenDayPct ?? 0) ? "five_hour" : "seven_day";
     }
 }