The app doesn't take advantage of the available horizontal space.

The app doesn't take advantage of the available horizontal space. On large screens, chat content is constrained to a narrow center column, so wide content like markdown tables requires horizontal scrolling despite ample empty space on both sides.

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| Field | Value |
| --- | --- |
| App version | 1.1.13 |
| OS | macOS 26.6.2 |
| Theme | Chai |
| Path | /chat |
| Tenure | Week 10 |

Start at the /chat view and reproduce the layout on a large macOS screen using the issue's markdown table example. Trace the chat content container and verify the fix by confirming that available horizontal space is used and wide tables no longer require unnecessary horizontal scrolling.

索引モデルが issue の本文から書いたものです。