feat(usage): add TokenTracker export models and test fixture

src/ClaudeDo.Worker/Usage/TokenTracker/TokenTrackerModels.cs

@@ -0,0 +1,66 @@
+namespace ClaudeDo.Worker.Usage.TokenTracker;
+
+/// <summary>One row of <c>tokentracker sessions --format json</c>. Field names mirror the
+/// export's <c>snake_case</c> keys: <c>cached_input_tokens</c> is the cache *read* count,
+/// <c>cache_creation_input_tokens</c> the write count.
+/// ⚠️ <paramref name="SessionHash"/> is <b>not</b> unique across rows — TokenTracker splits one
+/// Claude session into several rows (measured: 886 rows over 547 hashes), e.g. on a model switch.
+/// The segments are disjoint, so summing rows that share a hash is correct; counting them is not
+/// the same as counting sessions.</summary>
+public sealed record TokenTrackerSession(
+    string SessionHash,
+    string Source,
+    string Model,
+    DateTimeOffset StartedAt,
+    long InputTokens,
+    long OutputTokens,
+    long CacheReadTokens,
+    long CacheCreationTokens,
+    double CostUsd,
+    int Turns,
+    int RetryTurns,
+    bool Productive,
+    bool OneShot);
+
+/// <summary>A parsed export plus when we fetched it. <paramref name="FormatVersion"/> is the
+/// <c>version</c> field of the session rows — the only compatibility signal the export gives us.</summary>
+public sealed record TokenTrackerExport(
+    int FormatVersion,
+    IReadOnlyList<TokenTrackerSession> Sessions,
+    DateTime FetchedAtUtc);
+
+public sealed record TokenTrackerProbe(
+    bool Installed,
+    string? Version,
+    bool NodeOk,
+    string? NodeVersion,
+    string? Error)
+{
+    public static TokenTrackerProbe Unknown { get; } = new(false, null, false, null, null);
+}
+
+/// <summary>Outcome of one CLI invocation. <paramref name="Ok"/> false always carries an
+/// <paramref name="Error"/> — callers turn that into state, never into an exception.</summary>
+public sealed record TokenTrackerRunResult(bool Ok, string StdOut, string? Error);
+
+/// <summary>Aggregated per date/model/scope. <c>Scope</c> is <c>"claudedo"</c> or <c>"other"</c>,
+/// decided by whether the session hash belongs to one of our runs. <c>Sessions</c> replaces the
+/// old assistant-message count — it counts export <i>rows</i> (session segments), because the
+/// export has neither message granularity nor one row per session.</summary>
+public sealed record TokenTrackerModelRow(
+    DateOnly Date,
+    string Model,
+    string Scope,
+    long InputTokens,
+    long OutputTokens,
+    long CacheReadTokens,
+    long CacheCreationTokens,
+    int Sessions,
+    double CostUsd);
+
+/// <summary>What the export adds on top of what <c>task_runs</c> already knows about a task.</summary>
+public sealed record TokenTrackerTaskExtras(
+    double CostUsd,
+    int Retries,
+    bool Productive,
+    bool OneShot);