test(hooks): add additional test coverage for read-image-resizer hook

[Hungdoan565]

Add 5 additional edge case tests to the existing
ead-image-resizer/hook.test.ts:

• Non-string output handling
• Attachment without filename (fallback naming)
• Error handling during image processing
• Multiple attachments with mixed statuses

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Summary by cubic

Add five edge‑case tests for the read-image-resizer hook to improve reliability and coverage. Covers fallback filenames, skipping non‑string output, MIME type case normalization, and mixed outcomes across multiple attachments; also syncs bun.lock to bump oh-my-opencode platform binaries to 4.5.1.

^{Written for commit a525b46. Summary will update on new commits. Review in cubic}