Update Working Memory

Write the Working Memory file from user edits.

Validates structure, writes to ~/ai-now/memory.md, and emits a feed event with edited_by="user" to distinguish from agent-generated updates.

curl -X PUT "http://127.0.0.1:14242/agent/working-memory" \  -H "Content-Type: application/json" \  -d '{    "content": "string"  }'

{}

{
  "detail": [
    {
      "loc": [
        "string"
      ],
      "msg": "string",
      "type": "string",
      "input": null,
      "ctx": {}
    }
  ]
}