Remove ORAS manifest delete from merge workflow

[ianpittwood]

Summary

The OrasManifestDelete command frequently failed when cleaning up the temporary manifest index after a merge. This removes the command and the in-line cleanup step from OrasMergeWorkflow.

The temporary index is now left in place and cleaned up out-of-band by the clean.yml workflow (bakery clean temp-registry), which each product repo already runs on a schedule.

Changes

• Removed the OrasManifestDelete class from oras.py.
• Removed "Step 3" (delete temporary index) from OrasMergeWorkflow.run(); the workflow now only creates the temporary index and copies it to destinations.
• Updated the workflow docstring/comments to note the temp index is cleaned up by clean.yml.
• Updated tests: dropped the OrasManifestDelete import, removed TestOrasManifestDelete and test_manifest_delete_with_plain_http, and adjusted test_execute_success's call-count assertion from 4 → 3.

Testing

• uv run pytest test/plugins/builtin/oras/ → 43 passed
• uv run ruff check on both modified files → all checks passed

Notes

With the in-line delete gone, temporary indexes now persist until the cleanup job runs (default: removes those older than 3 days) rather than being deleted immediately after each merge.

🤖 Generated with Claude Code

[github-actions]

Test Results

1 568 tests   1 568 ✅  8m 31s ⏱️
    1 suites      0 💤
    1 files        0 ❌

Results for commit 6c8b7d0.