Summary

• add a centralized memory-sync hygiene guard in MemoryManager
• drop obvious Hermes framework artifacts per side before provider sync
• drop raw base64 media payloads while preserving normalized media markers from fix(memory): normalize multimodal sync content #32030
• cap excessive synced turn content at 8k chars

Stack

Draft and stacked on #32030. Please review/merge #32030 first; this follow-up is intentionally framed as provider-agnostic memory hygiene rather than Honcho-specific behavior.

Test Plan

• pytest tests/agent/test_memory_provider.py tests/agent/test_memory_session_switch.py tests/honcho_plugin/test_session.py::TestConcludeToolDispatch -q

Refs #3943