feat(worker): add TranscriptUsageReader for per-model token usage

Aggregates ~/.claude/projects/**/*.jsonl assistant messages by date/model/
scope (ClaudeDo worktree-or-sandbox cwd vs Other), deduped by requestId
(falls back to message.id), with a per-file length+mtime cache so repeat
calls skip unchanged files.

src/ClaudeDo.Worker/CLAUDE.md

@@ -19,6 +19,7 @@ Worker/
   Hub/          — WorkerHub, HubBroadcaster
   Logging/      — LogRingBuffer (30-min in-memory log window) + BroadcastLogSink (Serilog sink → footer + overlay)
   Report/       — ClaudeHistoryReader, WeekReportPromptBuilder, WeekReportService; interfaces in Report/Interfaces/
+  Usage/        — TranscriptUsageReader: aggregates Claude Code transcript token usage (~/.claude/projects/**/*.jsonl) by date/model/scope (ClaudeDo vs Other), deduped by requestId, with a per-file (length+mtime) cache; interface in Usage/Interfaces/
   Prime/        — daily-prep ("Prime Claude"): PrimeScheduler (BackgroundService), PrimeRunner (runs the daily prep), DailyPrepPrompt (fixed prompt + CLI args + LogPath() helper), NextDueCalculator, PrimeScheduleSignal; interfaces in Prime/Interfaces/ (IPrimeRunner, IPrimeClock, IPrimeScheduleSignal, IPrimeBroadcaster)
   Online/       — optional Online Inbox sync: OnlineInboxConfig (config record), Dtos (RemoteList/RemoteTask/MirrorTask), IOnlineInboxApi, OnlineInboxApiClient (typed HttpClient, bearer auth, HTTPS guard), OnlineTokenStore (DPAPI refresh-token store, Windows-only), StaticTokenAuthProvider (default/test IOnlineAuthProvider), ZitadelAuthProvider (OIDC discovery + refresh-token flow), OnlineSyncService (BackgroundService: reconcile loop), OnlineBacklog (Idle-backlog filter/query); interface in Online/Interfaces/ (IOnlineAuthProvider)
 ```