Agent Host Codex file-read completions intermittently omit result text

## Description

The Agent Host Codex E2E suite intermittently reports successful file-read tool completions with an empty `text` field, even though the turn response contains the expected file value. This makes the tool-result assertions fail for:

- `reads a file from a nested directory`
- `reads a value from JSON`

Observed completion payload:

```json
{"success":true,"text":""}
```

## Failing runs

- https://github.com/microsoft/vscode/actions/runs/31132506547/job/92724492870?pr=329485
- https://github.com/microsoft/vscode/actions/runs/31130785836/job/92718953820?pr=329492

## Expected

Successful Codex `Read`/`view`/`shell` completion notifications include the file contents in the result text so the protocol-level oracle can verify the operation.

## Temporary mitigation

Skip these two cases for Codex only. Keep them enabled for other providers while the missing completion text is investigated.