failed to post PR comment: Body is too long (maximum is 65536 characters)

### Describe the Bug

We had a PR that affected many components. Unfortunately Atmos is failing to post PR comment.

```
WARN CI aggregate PR comment skipped
error=
│ failed to post PR comment: POST https://api.github.com/repos/foo/bar/issues/123/comments: 422 Validation Failed [{Resource:IssueComment Field:data Code:unprocessable Message:Body is too long (maximum is 65536 characters)}]
│ (1) forced error mark
│ | "failed to post PR comment"
│ | errors/*errors.errorString::
│ Wraps: (2) failed to post PR comment: POST https://api.github.com/repos/foo/bar/issues/123/comments: 422 Validation Failed [{Resource:IssueComment Field:data Code:unprocessable Message:Body is too long (maximum is 65536 characters)}]
│ └─ Wraps: (3) POST https://api.github.com/repos/foo/bar/issues/123/comments: 422 Validation Failed [{Resource:IssueComment Field:data Code:unprocessable Message:Body is too long (maximum is 65536 characters)}]
│ └─ Wraps: (4) failed to post PR comment
│ Error types: (1) *markers.withMark (2) *fmt.wrapErrors (3) *github.ErrorResponse (4) *errors.errorString
```

### Expected Behavior

Atmos handles the error gracefully. Maybe splitting the content into multiple comments.

### Steps to Reproduce

Create a PR that triggers huge terraform diff across many stacks/components.

### Screenshots

_No response_

### Environment

_No response_

### Additional Context

_No response_

Start at the CI aggregate PR comment path and the GitHub issue-comment POST that produces the 65,536-character error. Reproduce it with a PR containing a large Terraform diff across many stacks or components; done means Atmos handles oversized output gracefully, such as by splitting it into multiple comments.

Written by the indexing model from the issue text.