Multiple inserts on one Strata instance

Can't seem to insert multiple records into the b-tree, looks like i always need to create a new instance to insert

```bash
AN ERROR? Journalist.Error: ALREAY_COMMITTED

stack:

at Journalist.mkdir (/Users/sochimabiereagu/Stuff/Personal/code/ipdb/node_modules/.pnpm/journalist@0.1.31/node_modules/journalist/journalist.js:137:26)
at FileSystem.Writer.writeSplitLeaf (.../filesystem.js:433:20)
at async Sheaf._splitLeaf (.../sheaf.js:679:13)
at async Sheaf._keephouse (.../sheaf.js:961:25)
at async Sheaf._fractured (.../sheaf.js:980:17)
at async Destructible._awaitPromise (.../node_modules/.pnpm/destructible@7.0.0-alpha.72/node_modules/destructible/destructible.js:558:24) {
[errors]: []
}
AN ERROR? Destructible.Error: strand exited with exception

{
"code": "ERRORED",
"id": "queue",
"countdown": 0,
"waiting": []
}

cause:

Destructible.Error: strand exited with exception

{
"code": "ERRORED",
"method": "ephemeral",
"id": "worker"
}
```

Start by reproducing multiple inserts on one Strata instance and follow the reported stack from filesystem.js:433, through Sheaf._splitLeaf and Sheaf._keephouse in sheaf.js. Compare the first and subsequent leaf-split writes, focusing on the Journalist.mkdir ALREADY_COMMITTED error. Done means repeated inserts complete without the reported writer and queue errors.

Written by the indexing model from the issue text.