fix(sqlite): shim db.transaction(fn) on node:sqlite DatabaseSync

[leiverkus]

Follow-up to #121.

Summary

bun:sqlite and better-sqlite3 both expose db.transaction(fn) which returns a callable that wraps fn in BEGIN/COMMIT (auto-ROLLBACK on throw). node:sqlite's DatabaseSync has no equivalent.

handleAddMemory (services/api-handlers.ts) and client.addMemory (services/client.ts) both use this method to atomically insert a memory row, so under Node:

• POST /api/memories crashes with db.transaction is not a function
• Any auto-capture path that promotes a candidate memory crashes the same way

Reproduced today on opencode 1.15.10 (anomalyco fork) + Node sidecar:

$ curl -X POST http://127.0.0.1:4747/api/memories \
    -H 'Content-Type: application/json' \
    -d '{"content": "test", "containerTag": "scope-project-xxx", "type": "fact"}'
{"success":false,"error":"TypeError: db.transaction is not a function"}

(After patching the sharp install separately — opencode-mem still ships @xenova/transformers which needs sharp's native binary, but that's a pre-existing packaging issue, not in scope here.)

Fix

Subclass DatabaseSync to add a transaction(fn) method matching the bun:sqlite / better-sqlite3 signature. Single-mode (BEGIN) semantics only — the .deferred / .immediate / .exclusive variants are not exercised by this codebase, can be added in a follow-up if needed.

transaction<Fn extends (...args: unknown[]) => unknown>(fn: Fn): Fn {
  const self = this;
  const wrapped = function (this: unknown, ...args: Parameters<Fn>): ReturnType<Fn> {
    self.exec("BEGIN");
    try {
      const result = fn.apply(this, args) as ReturnType<Fn>;
      self.exec("COMMIT");
      return result;
    } catch (err) {
      try {
        self.exec("ROLLBACK");
      } catch {
        /* best-effort rollback after partial state */
      }
      throw err;
    }
  };
  return wrapped as unknown as Fn;
}

Why it slipped through #121

My local E2E smoke test exercised CRUD via prepared statements but never called db.transaction(). The Bun test suite covers a lot of surface but doesn't reach the bun:sqlite-specific transaction path in a Node-runtime-only context. Today's session log on the live Node sidecar surfaced the gap immediately on the first POST /api/memories.

Verification

• bun test: 143 pass / 0 fail (Bun path unchanged)
• bun run typecheck: clean
• bun run build: clean
• npx prettier --check: clean
• Node 26 E2E with commit + rollback paths:
  • Successful tx commits both inserts → SELECT * FROM m returns both rows
  • Failing tx throws after one insert → SELECT still shows the pre-tx state (rollback worked)
• Local patch applied to the cached v2.15.0 install → POST /api/memories now returns {success:true} as expected.

Environment

• macOS 26.3 (Apple Silicon, arm64)
• opencode 1.15.10 CLI / 1.15.13 Desktop (anomalyco fork)
• opencode-mem 2.15.0 (with fix(runtime): support Node plugin loader (bun:sqlite + Bun.serve fallbacks) #121 merged)
• Node 26.0.0 (DatabaseSync stable)