"unsupported startup parameter": the client sends what Neon rejects

# "unsupported startup parameter": diagnose and fix

## Symptom
Connection fails immediately with `unsupported startup parameter: [parameter-name]`.

## Cause
Some clients/drivers send extra startup parameters on connect (common with newer drivers sending options the proxy allowlist does not include). Neon's proxy rejects unknown startup parameters instead of ignoring them.

## Confirm
1. The parameter name in the error; check whether your driver added it by default or via config.
2. Other clients without that parameter connect fine with the same string.

## Fix
- Remove or override the parameter in the client configuration/connection options.
- If the driver requires it, check the driver's docs for a compatibility flag; as a last resort use a different driver version.
- Report it: parameters that mainstream drivers send by default are worth flagging to Neon support.

## Verify
The client connects with no startup-parameter error and behaves normally afterwards.