feat(FN-4389): complete Step 2 — add schema migration for cache write tokens

Fusion-Task-Id: FN-4389
Fusion-Task-Lineage: 366f9d57-c476-448f-96c0-6e753fc8b090

packages/core/src/db.ts

@@ -119,7 +119,7 @@ export function probeFts5(db: DatabaseSync): boolean {
 
 // ── Schema Definition ────────────────────────────────────────────────
 
-const SCHEMA_VERSION = 73;
+const SCHEMA_VERSION = 74;
 
 function normalizeTaskComments(
   steeringComments: SteeringComment[] | undefined,
@@ -220,6 +220,7 @@ CREATE TABLE IF NOT EXISTS tasks (
   tokenUsageInputTokens INTEGER,
   tokenUsageOutputTokens INTEGER,
   tokenUsageCachedTokens INTEGER,
+  tokenUsageCacheWriteTokens INTEGER,
   tokenUsageTotalTokens INTEGER,
   tokenUsageFirstUsedAt TEXT,
   tokenUsageLastUsedAt TEXT,
@@ -3157,6 +3158,12 @@ export class Database {
       });
     }
 
+    if (version < 74) {
+      this.applyMigration(74, () => {
+        this.addColumnIfMissing("tasks", "tokenUsageCacheWriteTokens", "INTEGER");
+      });
+    }
+
   }
 
   /**