Data race on close

Describe the bug

We encountered a data race in our automated tests. It is potentially difficult to replicate but here is the stack trace.

WARNING: DATA RACE
Read at 0x00c000b64d30 by goroutine 2204:
  runtime.chansend()
      /opt/hostedtoolcache/go/1.25.5/x64/src/runtime/chan.go:176 +0x0
  github.com/dgraph-io/badger/v4.(*DB).sendToWriteCh()
      /home/runner/go/pkg/mod/github.com/dgraph-io/badger/v4@v4.8.0/db.go:904 +0x3c4
  github.com/dgraph-io/badger/v4.(*Txn).commitAndSend()
      /home/runner/go/pkg/mod/github.com/dgraph-io/badger/v4@v4.8.0/txn.go:593 +0x15d8
  github.com/dgraph-io/badger/v4.(*Txn).Commit()
      /home/runner/go/pkg/mod/github.com/dgraph-io/badger/v4@v4.8.0/txn.go:663 +0x218

Previous write at 0x00c000b64d30 by goroutine 1311:
  runtime.closechan()
      /opt/hostedtoolcache/go/1.25.5/x64/src/runtime/chan.go:414 +0x0
  github.com/dgraph-io/badger/v4.(*DB).close()
      /home/runner/go/pkg/mod/github.com/dgraph-io/badger/v4@v4.8.0/db.go:550 +0x31c
  github.com/dgraph-io/badger/v4.(*DB).Close.func1()
      /home/runner/_work/defradb/defradb/internal/db/store.go:149 +0x2c5

To Reproduce

Steps to reproduce the behavior:

Test badger with -race.

Expected behavior

No data race present.

Screenshots

N/A

Environment

Runner info available here: https://github.com/sourcenetwork/defradb/actions/runs/20442873100/job/58739759303?pr=4212

Additional context

N/A

The race involves DB.close in db.go and transaction commit paths in txn.go, with the caller stack also naming internal/db/store.go. Start by testing Badger with -race and tracing the close/send paths; done means the reported data race no longer appears.