chore(db): enable auto-vacuum and add periodic maintenance

One-time migration: detect auto_vacuum = 0 (NONE) and switch to
INCREMENTAL. Run a full VACUUM to apply the mode change. Subsequent
database opens skip this since the mode persists.

This prevents the database file from growing indefinitely as deleted
rows leave behind free pages that are never reclaimed.

Author: BYK

packages/core/src/database/database.ts

@@ -3,6 +3,7 @@ export * as Database from "./database"
 import { EffectDrizzleSqlite } from "@opencode-ai/effect-drizzle-sqlite"
 import { layer as sqliteLayer } from "#sqlite"
 import { Context, Effect, Layer } from "effect"
+import { sql } from "drizzle-orm"
 import { Global } from "../global"
 import { Flag } from "../flag/flag"
 import { isAbsolute, join } from "path"
@@ -30,6 +31,14 @@ const layer = Layer.effect(
     yield* db.run("PRAGMA cache_size = -64000")
     yield* db.run("PRAGMA foreign_keys = ON")
     yield* db.run("PRAGMA wal_checkpoint(PASSIVE)")
+
+    // One-time migration: enable incremental auto-vacuum (takes effect after next VACUUM)
+    const autoVacuumMode = yield* db.get<{ auto_vacuum: number }>(sql`PRAGMA auto_vacuum`)
+    if (autoVacuumMode?.auto_vacuum === 0) {
+      yield* db.run("PRAGMA auto_vacuum = INCREMENTAL")
+      yield* db.run("VACUUM")
+    }
+
     yield* DatabaseMigration.apply(db)
 
     return { db }