[Bug] Large assistant messages duplicate in terminal output

Bug Description

• OS: macOS Darwin 25.4.0 - Shell: zsh - 症状: 大きな（数百行）アシスタントメッセージが terminal scrollback に複数回重複描画される - 再現: 直前の Issue 草案の出力時 - 影響: 内容自体は正しいが視認性が悪化

Environment Info

• Platform: darwin
• Terminal: vscode
• Version: 2.1.119
• Feedback ID: 4baab337-dac3-4678-8c30-7438fc4ce87b

Errors

[{"error":"McpError: MCP error -32603: MCP error -32603: Failed to get teams: GraphQL operation failed: It looks like you're trying to use an API key as a Bearer token. Remove the Bearer prefix from the Authorization header.\n    at fromError (/$bunfs/root/src/entrypoints/cli.js:93:45042)\n    at _onresponse (/$bunfs/root/src/entrypoints/cli.js:97:22808)\n    at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:97:18446)\n    at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:4829:14236)\n    at processReadBuffer (/$bunfs/root/src/entrypoints/cli.js:842:29664)\n    at <anonymous> (/$bunfs/root/src/entrypoints/cli.js:842:29269)\n    at emit (node:events:95:22)\n    at addChunk (internal:streams/readable:264:47)\n    at readableAddChunkPushByteMode (internal:streams/readable:242:18)\n    at handleNumberResult (internal:streams/native-readable:69:18)","timestamp":"2026-04-27T02:22:18.677Z"}]