Run oxfmt across repo, add format script and ignore config

Format all non-generated files with oxfmt via `vp fmt`. Add
.oxfmtignore to skip bindings/ and wasm-pack output. Add npm
format script and update DEVELOPMENT.md docs.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src-web/lib/minPromiseMillis.ts

@@ -1,4 +1,4 @@
-import { sleep } from './sleep';
+import { sleep } from "./sleep";
 
 /** Ensures a promise takes at least a certain number of milliseconds to resolve */
 export async function minPromiseMillis<T>(promise: Promise<T>, millis = 300) {