Revert #2574 (notify-based runner-lock wake) once rocksdb-js with #849 is pinned

#2574 is a **temporary workaround**, not the design. It takes the derived-index runner lock without an unlock callback and wakes waiting runners through the readiness buffer's `notify()`, a self-notification skip, and a 5 s retry timer — because with the pinned rocksdb-js, a `tryLock(key, callback)` waiter queued by a worker that is later `terminate()`d aborts the process on Node 22 when another thread unlocks ([rocksdb-js#848](https://github.com/HarperFast/rocksdb-js/issues/848)). That is a bug in the primitive, fixed at the root by [rocksdb-js#849](https://github.com/HarperFast/rocksdb-js/pull/849) (a dying env's queued lock callbacks are released from its cleanup hook; the release paths hold `locksMutex` across the tsfn calls).

The lock's own unlock callback is the simpler and more correct wake: one primitive, and a holder that dies releases natively and wakes the waiters immediately, where the workaround waits for a commit or up to 5 s. Once the fix is pinned, revert.

## Checklist

- [ ] rocksdb-js release containing #849 is published
- [ ] `@harperfast/rocksdb-js` pin bumped in harper `main` (and any release line that took #2574)
- [ ] revert #2574 (`git revert`, resolving `resources/derivedIndexRuntime.ts` back to `tryLock(this.#lockKey, retry)` and dropping `#skipNextNotify` / `#lockBackoff` / `LOCK_RETRY_MILLISECONDS`; restore the removed "synchronous unlock callback" test in `derivedIndexRuntime.test.js`)
- [ ] `unitTests/resources/vectorIndexPlane.test.js` passes on **Node 22** with the new pin and the callback path (this is the suite that aborted `main`'s Node 22 CI)
- [ ] `DESIGN.md § Derived-index runtime › Ownership and wake-up`: replace the "Temporarily … tracked revert" paragraph with the callback description and a one-line note that the notify path existed until rocksdb-js ⟨version⟩

Verification that the fix alone suffices: `main`'s runtime unchanged against a #849 binary passes `vectorIndexPlane.test.js` 22/22 on Node 22.23.1.

Refs #2574, #2430, #2489.

First confirm that a published rocksdb-js release contains #849 and inspect resources/derivedIndexRuntime.ts, derivedIndexRuntime.test.js, and DESIGN.md § Derived-index runtime › Ownership and wake-up. Run unitTests/resources/vectorIndexPlane.test.js on Node 22 with the new pin. Done means reverting #2574, restoring the synchronous unlock callback test, updating the design note, and passing the Node 22 suite.

Written by the indexing model from the issue text.