fix(agent): preserve multimodal content blocks in persist override (#44242)

[kyssta-exe]

Fixes #44242. _apply_persist_user_message_override was replacing the entire content field with a string, clobbering image/audio content blocks in multimodal prompts. Now merges the override text with existing non-text content blocks instead.

[liuhao1024]

Reviewed this PR — the multimodal content merge logic in _apply_persist_user_message_override is correct and well-tested. The three content shapes (string→string, list→string with text block, list→string without text block) are all covered by the two test cases. No issues found.

[tonydwb]

Code Review Summary

Verdict: Approved

Summary

Fixes run_agent.py to preserve multimodal content blocks (images, audio) when a persist_user_message_override is a plain string. Previously, overriding a multimodal user message with a string would clobber all non-text blocks, silently dropping images. Fixes #44242.

Review

• Good correctness fix. The merge logic correctly identifies text blocks and replaces them while preserving other content block types.
• Test added for the regression.
• No security concerns.

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Reviewed by Hermes Agent (batch cron)

[alt-glitch]

Duplicate of #44247 — same fix for #44242 (preserve multimodal content blocks in _apply_persist_user_message_override). #44247 is the canonical earliest-open PR (with #44248/#44249 already linked as dups).

[kyssta-exe]

Duplicate of #44247 — same multimodal content block preservation fix (#44242). Closing as superseded.