ERROR FIXED:
- FileNotFoundError on deleted session files caused 2,551 restarts/24h
- Embedding token overflow for long messages (exceeded 4K token limit)
ROOT CAUSES:
1. File opened before existence check - crash when OpenClaw deletes session files
2. No content truncation for embedding - long messages failed silently
FIXES:
1. Added pre-check for file existence before open()
2. Added try/catch for FileNotFoundError
3. Added chunk_text() for long content (6000 char chunks with 200 char overlap)
4. Each chunk stored separately with metadata (chunk_index, total_chunks)
IMPACT:
- Eliminates crash loop
- No memory loss for long messages
- Graceful recovery on session rotation
