refactor(usage): drop the transcript aggregation path in favour of TokenTracker

src/ClaudeDo.Worker/Usage/UsageModels.cs

@@ -17,22 +17,6 @@ public sealed record UsageSnapshot(
     IReadOnlyList<UsageLimitRow> Limits,
     DateTime FetchedAtUtc);
 
-public enum UsageScope
-{
-    ClaudeDo,
-    Other,
-}
-
-public sealed record UsageAggregateRow(
-    DateOnly Date,
-    string Model,
-    UsageScope Scope,
-    long InputTokens,
-    long OutputTokens,
-    long CacheReadTokens,
-    long CacheCreationTokens,
-    int Messages);
-
 /// <summary>Cumulative raw token usage for one Claude Code session (all its transcript
 /// lines to date), synthetic messages excluded. Not a per-run delta.</summary>
 public sealed record SessionUsageTotals(