[ARI-32] Create test incident set (10 diverse incidents)

[bjridicodes]

Linear: ARI-32

Type: ⚙️ Enabler | Sprint: 7 | Points: 3

As a Data Platform OPS engineer, I want a set of 10 test incidents covering diverse platforms and error types so that acceptance criteria can be validated consistently and repeatably.

Acceptance Criteria

Given the test incident set is created
When reviewed
Then it covers at least 4 different platform tags (cdp, databricks, oracle, gcp or aws)
And at least 5 different error classes (OOM, disk_full, network_timeout, auth_failure, pipeline_failure)

Given the test incident set is created
When loaded into the test fixtures
Then all 10 have realistic short_description, long_description, affected_ci, and opened_at fields

Given the test incident set is created
Then corresponding log fixtures exist for at least 8 of the 10 incidents (2 may have no logs to test AC-03 graceful handling)