[Bug]: CouchDB 3.5.1 upgrade leads to elevated memory and instability (OOM on single node + full cluster drop during rolling upgrade)

### Version

3.5.1

### Describe the problem you're encountering

After upgrading from CouchDB 3.4.2 -> 3.5.1, we are seeing stability regressions in both:
- Single node environments (OOM kill crash)
- 3 node clustered environments (full cluster outage during rolling upgrade)
These environments were stable on 3.4.2 under same workloads
The main symptoms include:
- Increased Erlang VM RSS memory usage (beam.smp)
- Very large Erlang process counts post-upgrade
- CPU spikes during compaction/rebalancing
- Cluster becoming unavailable during node cycling

### Expected Behaviour

- CouchDB 3.5.1 should not significantly increase baseline memory/process usage on the same workload
- Single node instances should not be OOM killed under normal compaction load
- Rolling node upgrades should not result in full cluster outage

### Steps to Reproduce

We have observed the issues under the following conditions:
- Upgrade CouchDB 3.4.2 → 3.5.1 (Erlang/OTP 26)
- Run with medium memory nodes (~8GB RAM)
- Large shard count / very high DB count
- Compaction or shard movement occurring
- Cycle one node during rolling upgrade (ASG refresh)

Result: memory/process growth and potential node loss -> cluster unavailability

### Your Environment

Deployment

- AWS EC2 instances with persistent couch_data
- CouchDB nodes managed via ASG refresh (one node at a time)
- HAProxy + Fauxton access through fronted endpoint

Cluster configuration:
- 3-node cluster (n=3, q=1)
- Placement: primary / secondary / trinary
- Data size: ~319k databases
- Disk usage: ~640GB used of ~1TB per node

Instance resources:
~7.6GB RAM

### Additional Context

_No response_

No source file, test, or entry point is named. Start by reproducing the 3.4.2-to-3.5.1 upgrade with Erlang/OTP 26 under high shard and database counts, then measure beam.smp memory, process counts, compaction, and rolling node cycling; done means identifying the regression and preventing OOM or cluster-wide unavailability.

Written by the indexing model from the issue text.