Description

In the with_mongot_extension_hybridSearch_disabled_* suite family (all four topologies:
single_node, single_shard, sharded_cluster, sharded_collections), the e2e test
jstests/with_mongot/e2e/hybridSearch/union_with_vector_search.js fails with:

Location51047: $vectorSearch is not allowed within a $lookup's sub-pipeline

This is a test bug, not a server bug

The rejection is correct behavior. This family runs with
featureFlagExtensionsInsideHybridSearch: false, under which extension $vectorSearch is
legitimately not permitted inside a $lookup sub-pipeline. The test (added for SERVER-96412) exercises
hybrid patterns that combine $search and $vectorSearch via $unionWith and $lookup, and some of those
cases place $vectorSearch inside a $lookup sub-pipeline – which only works when
featureFlagExtensionsInsideHybridSearch is enabled.

The test must be updated to *skip its $lookup-sub-pipeline $vectorSearch cases when
featureFlagExtensionsInsideHybridSearch is disabled* (guard on the feature flag). The $unionWith cases
should continue to run.

Current mitigation

The whole file is excluded from the hybridSearch_disabled family via a new override block
exclude_extensions_inside_hybrid_search_disabled_incompatible in
buildscripts/resmokeconfig/matrix_suites/overrides/with_mongot_extension.yml. Once the test is
fixed to skip the disallowed cases under the flag, remove that exclusion so the $unionWith coverage
runs again in this family.

Repro

buildscripts/resmoke.py run --suites=with_mongot_extension_hybridSearch_disabled_single_node \
--continueOnFailure --excludeWithAnyTags=incompatible_with_amazon_linux,requires_external_data_source \
--jobs=4 --shuffle --modules=none --storageEngineCacheSizeGB=1 \
jstests/with_mongot/e2e/hybridSearch/union_with_vector_search.js

Fails on all four hybridSearch_disabled topologies; passes in search_disabled / vectorSearch_disabled
families (where the flag is on).