Describe the bug

$graphLookup over a collection that has a wildcard index fails with CommandNotSupported: Unrecognized BSON data type code 0. The same query succeeds once the wildcard index is dropped. The wildcard index is on an unrelated path, not on connectFromField or connectToField.

Environment

• Operating system and version: documentdb-local Docker image, Debian GNU/Linux 13 (trixie), image ghcr.io/documentdb/documentdb/documentdb-local:latest (sha256:4a341daca29b…, DocumentDB 1.0.0), host macOS 26.6.2 with OrbStack (Docker 29.8.2)
• PostgreSQL version: 17.11
• Architecture: arm64 (aarch64)

Reproduction Steps

const t = db.getSiblingDB("repro_graphlookup")
t.people.insertMany(Array.from({ length: 20000 }, (_, i) => ({
  _id: i,
  manager_id: i > 100 ? Math.floor(i / 10) : null,
  custom: { dept: "d" + (i % 50), level: i % 5 }
})))

const pipeline = [
  { $match: { _id: 19999 } },
  { $graphLookup: { from: "people", startWith: "$manager_id", connectFromField: "manager_id",
                    connectToField: "_id", as: "chain", maxDepth: 5 } },
  { $project: { n: { $size: "$chain" } } }
]

t.people.aggregate(pipeline).toArray()        // OK
t.people.createIndex({ "custom.$**": 1 })
t.people.aggregate(pipeline).toArray()        // fails
t.people.dropIndex("custom.$**_1")
t.people.aggregate(pipeline).toArray()        // OK again

Expected behavior

The query returns the same result with or without the wildcard index ([ { _id: 19999, n: 3 } ]), as on MongoDB 9.0.4.

Actual behavior

With the wildcard index present:

MongoServerError[CommandNotSupported]: Unrecognized BSON data type code 0

Without it, or with only a regular index on manager_id, the result is correct.

Additional context

#769 item 1 reports the same error on $lookup and infers that a wildcard index on the foreign collection triggers it, without isolating it. In our testing, a plain $lookup and a let/pipeline $lookup into a collection with a wildcard index both worked on 1.0.0, while $graphLookup fails every time. This repro isolates the trigger.

Related: #769.