Messages show incorrect author attribution - all messages appear from viewing user

[sanity]

Bug Description

When users exchange messages in a River room, all messages appear to be authored by the viewing user rather than their actual authors. This results in incorrect message attribution where User1's messages appear as if they were sent by User2 when User2 views them.

Steps to Reproduce

1. Create a River room with User1
2. Invite User2 to the room
3. User1 sends a message: "Test message from user1"
4. User2 sends a message: "Test message from user2"
5. When either user lists messages, all messages show the viewing user's author ID and nickname

Expected Behavior

• User1's messages should show User1's author ID and nickname
• User2's messages should show User2's author ID and nickname
• Each message should maintain its original author attribution regardless of who is viewing

Actual Behavior

All messages show the same author ID and nickname - that of the user viewing the messages:

[
  {
    "author": "L2OQWJ2M",
    "content": "Test message from user1 at 2025-07-30 19:21:08.000830",
    "nickname": "User2",
    "timestamp": "2025-07-31T00:21:08.016333835+00:00"
  },
  {
    "author": "L2OQWJ2M",
    "content": "Test message from user2 at 2025-07-30 19:21:08.140470",
    "nickname": "User2",
    "timestamp": "2025-07-31T00:21:08.158373159+00:00"
  }
]

Both messages incorrectly show:

• Same author ID: "L2OQWJ2M"
• Same nickname: "User2"

Impact

This bug makes it impossible to distinguish who sent which message in a conversation, breaking the fundamental chat functionality.

Additional Context

This issue was discovered while debugging River functionality with the Freenet gateway. The gateway connection issues have been resolved (see freenet/freenet-core#1731), but this River attribution bug remains.

Environment

• Freenet version: v0.1.20+ with gateway fix
• River version: latest main branch
• Testing via gateway connection

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