Stabilizes the Intercom transport-error spec when Rails reloads
application constants during the full backend suite. The production
client behavior is unchanged; the expectation now compares the exception
class name while continuing to verify its message and metadata.
## Closes
- Follow-up to
[CW-7615](https://linear.app/chatwoot/issue/CW-7615/optimize-intercom-import-reliability-and-bulk-message-ingestion)
- Follow-up to #15050
## How to reproduce
1. Run the backend shard containing the Intercom client spec after specs
that trigger Rails constant reloading.
2. Observe that the old matcher can reject an exception whose printed
class is still `DataImports::Intercom::Client::Error` because it
references a different class object.
3. Confirm the updated expectation accepts the reloaded class by name
and still verifies the transport error message and body.
## What changed
- Compare the raised Intercom client error using `error.class.name`.
- Preserve assertions for the user-facing error message and transport
error metadata.
## Checklist
- [x] My code follows the style guidelines of this project
- [x] I have performed a self-review of my code
- [x] New and existing focused unit tests pass locally with my changes
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