feat(db): Bun.SQL connection and portable migrations

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

packages/db/src/connect.ts

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+import { mkdirSync } from "node:fs";
+import { dirname } from "node:path";
+
+export type Db = { sql: Bun.SQL; dialect: "sqlite" | "postgres"; close(): Promise<void> };
+
+export async function connect(url: string): Promise<Db> {
+  if (url.startsWith("sqlite:")) {
+    const path = url.replace(/^sqlite:(\/\/)?/, "");
+    if (path !== ":memory:" && path !== "") mkdirSync(dirname(path), { recursive: true });
+    // A single connection keeps in-memory databases coherent and serialises writers.
+    const sql = new Bun.SQL(url, { max: 1 });
+    await sql.unsafe("PRAGMA foreign_keys = ON");
+    if (path !== ":memory:") await sql.unsafe("PRAGMA journal_mode = WAL");
+    return { sql, dialect: "sqlite", close: () => sql.close() };
+  }
+  if (url.startsWith("postgres:") || url.startsWith("postgresql:")) {
+    const sql = new Bun.SQL(url);
+    return { sql, dialect: "postgres", close: () => sql.close() };
+  }
+  throw new Error(`Unsupported database URL (expected sqlite:// or postgres://): ${url}`);
+}

packages/db/src/index.ts

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+export { connect, type Db } from "./connect";
+export { migrate } from "./migrate";

packages/db/src/migrate.ts

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+import { readdirSync, readFileSync } from "node:fs";
+import { join } from "node:path";
+import type { Db } from "./connect";
+
+const MIGRATIONS_DIR = join(import.meta.dir, "..", "migrations");
+
+function statements(text: string): string[] {
+  const noComments = text.split("\n").filter((l) => !l.trim().startsWith("--")).join("\n");
+  return noComments.split(";").map((s) => s.trim()).filter(Boolean);
+}
+
+export async function migrate(db: Db): Promise<string[]> {
+  await db.sql.unsafe("CREATE TABLE IF NOT EXISTS schema_migrations (name TEXT PRIMARY KEY, applied_at TEXT NOT NULL)");
+  const done = new Set((await db.sql`SELECT name FROM schema_migrations`).map((r: { name: string }) => r.name));
+  const files = readdirSync(MIGRATIONS_DIR).filter((f) => f.endsWith(".sql")).sort();
+  const applied: string[] = [];
+  for (const name of files) {
+    if (done.has(name)) continue;
+    const stmts = statements(readFileSync(join(MIGRATIONS_DIR, name), "utf8"));
+    await db.sql.begin(async (tx) => {
+      for (const s of stmts) await tx.unsafe(s);
+      await tx`INSERT INTO schema_migrations (name, applied_at) VALUES (${name}, ${new Date().toISOString()})`;
+    });
+    applied.push(name);
+  }
+  return applied;
+}