Add wa-sqlite browser backend for SQLite indexer

[marcus-pousette]

Goal

Add wa-sqlite (SQLite WASM) support so Peerbit can use a SQLite-backed indexer in the browser (ideally persisted via OPFS), without relying solely on @sqlite.org/sqlite-wasm.

Why

We want a browser-capable SQLite backend for indexing (documents/programs) with:

• good performance vs pure in-memory indices
• persistence (OPFS when available)
• better bundler/runtime ergonomics (Vite/etc)
• a path that works even when SharedArrayBuffer / cross-origin isolation is not available

Today @peerbit/indexer-sqlite3 already has a browser path via @sqlite.org/sqlite-wasm, but it comes with heavier initialization and constraints. Adding wa-sqlite gives us another implementation option and a fallback for environments where sqlite.org's OPFS/SAH pool approach is problematic.

Scope

A. New backend option

Either:

• add a new package (suggested): @peerbit/indexer-wa-sqlite, or
• add a selectable engine inside @peerbit/indexer-sqlite3 (e.g. { engine: 'sqlite.org' | 'wa-sqlite' }).

B. Storage/VFS options

• OPFS VFS (preferred when available)
• fallback VFS (memory or IDB) when OPFS is unavailable or locked

C. Worker model

• run SQLite in a Worker (similar to current proxy/worker model) to keep UI responsive
• expose a minimal proxy that implements @peerbit/indexer-interface

D. Tooling

• ensure wasm + worker assets work with the site build (Vite) and CI

Deliverables

• Browser demo/test that creates an index, writes rows, queries, and persists across reload (when OPFS is enabled)
• Basic perf sanity check vs current wasm backend (optional)

Acceptance criteria

• peerbit-org can use a SQLite-backed indexer in the browser without crashing and without special runtime assumptions.
• Indexer can be configured in apps (Document store / Peerbit.create indexer hook) to pick the wa-sqlite backend.
• Tests cover the basic read/write/query flow in a browser runtime.

Related

• documents: Allow for SQLLite WASM backend #275 (documents: allow a SQLite WASM backend)
• OPFS persistance with multiple tabs, prevent lock issues #304 (OPFS persistence across multiple tabs / lock issues)

[Faolain]

This would be huge!!

the COOP/COEP headers were some of my biggest problems with Peerbit and OPFS, finding where to host, and debugging issues that were only happening prod with sqlite vs dev