Table.deleteHistory() returns a non-zero count on RocksDB, where RocksTransactionLogStore.remove() is a no-op and nothing is deleted

`Table.deleteHistory()` returns a count of audit entries it did not delete when the table is on RocksDB.

`RocksTransactionLogStore.remove()` is a no-op — an `async remove() { /* TODO */ }` stub (`resources/RocksTransactionLogStore.ts`) — so `removeAuditEntry()` resolves without removing anything. `deleteHistory` increments `entriesDeleted` in its per-removal `onSuccess` callback either way, so a component author calling it on a RocksDB table gets a non-zero return for work that did not happen.

Found while reviewing #2458 (the audit staleness floor), which is why the floor deliberately is NOT raised on the RocksDB path there: nothing is actually pruned, so claiming it was would be worse than the misleading count.

## Why the obvious fix is wrong

An early `if (isRocksDB) return 0;` at the top of `deleteHistory` looks right and is not: the `cleanupDeletedRecords` branch calls `primaryStore.remove(key, version)`, which is real work on RocksDB and has a RocksDB-only regression test — `unitTests/resources/auditLog.test.js`, "RocksDB versioned removal preserves records recreated before or during removal", which `this.skip()`s *unless* `isPrimaryRocksDatabase` and calls `deleteHistory(Date.now() + 60_000, true)`. An early return would silently make that test dead and disable tombstone cleanup on the engine that needs it.

## Options

- Count only removals that actually removed something — needs `remove()` to report that, which it currently cannot.
- Return a shaped result that separates audit entries from tombstones (`{ auditEntriesDeleted, recordsDeleted }`), which is a breaking change to a public return value.
- Implement `RocksTransactionLogStore.remove()` so the count becomes true. The `TODO` there suggests this was always the intent; note that RocksDB prunes by whole log file, so per-entry removal may not be expressible.
- Document the return as "entries considered" and leave it.

Worth deciding which, since the return value is public API surface on a table.

Start by reading resources/RocksTransactionLogStore.ts and the Table.deleteHistory/removeAuditEntry implementation to understand the no-op removal and success counting. Run unitTests/resources/auditLog.test.js, including the RocksDB versioned-removal case. Done means the chosen public return behavior is implemented and tested without disabling cleanupDeletedRecords or its RocksDB regression coverage.

Written by the indexing model from the issue text.