@claude review doesn't pick up new commits in the PR

**Describe the bug**
We use the [experimental review mode](https://github.com/anthropics/claude-code-action/blob/main/examples/claude-experimental-review-mode.yml), the only change we made is removed the `synchronize` trigger to control the costs.
When we open the PR, we get the review immediately. We then fix the issues and make another commit in the same pull request, and we comment "@claude review" in the PR. The review runs again, but it leaves the same comments as first time, not noticing that we fixed the issues.

**To Reproduce**
Steps to reproduce the behavior:

1. Copy the [experimental review mode](https://github.com/anthropics/claude-code-action/blob/main/examples/claude-experimental-review-mode.yml) action, and remove `synchronize` trigger.
2. Open a pull request with some obvious errors
3. Wait for the initial review to complete
4. Fix the errors spotted by Claude review
5. Comment "@claude review"
6. Observe how the same errors are reported even though you fixed them.

**Expected behavior**
"@claude review" should review the diff between PR branch and the base branch, not individual commits which get outdated.

**API Provider**

[x] Anthropic First-Party API (default)
[ ] AWS Bedrock
[ ] GCP Vertex