fix: ensure tool result content is always array format

[yjjheizhu]

Problem

OpenClaw core expects toolMsg.content to be an array of {type, text} objects. When the context compactor encounters a short tool result (≤6000 chars), it returns the original message unchanged. If msg.content is a raw string, the core code crashes:

toolMsg.content.filter is not a function

This causes the entire agent session to crash silently, losing all context and memory. The agent appears to "amnesia" after 2-3 rounds of conversation.

Root Cause

In contextCompactor, the short message path:

const text = typeof msg.content === "string" ? msg.content : JSON.stringify(...);
if (text.length <= TOOL_MAX) return msg;  // ← returns string content unchanged

The truncated path also returns a plain string:

return { ...msg, content: "truncated string" };  // ← wrong format

Fix

1. Extract text from both string and array content formats — properly handles {type: "text", text} array elements
2. Short messages: ensure content is always [{type: "text", text}] array format
3. Truncated messages: return array format instead of raw string
4. Avoid JSON.stringify on arrays — prevents double-encoding of structured content

Testing

Tested locally with graph-memory plugin loaded. Agent no longer crashes when context compactor processes tool results. Memory and conversation continuity preserved across multiple rounds.