🧩 Problem
When I collapse the left sidebar and the files panel, the chat area stays narrow.
Since the chat content isn't responsive, the conversation remains constrained to a
fixed (narrow) width, wasting the freed screen space.

This makes it harder to work with:
- 📊 Charts and tables generated in conversations
- 📝 Code blocks / longer lines of text
- 🖼️ Wide images and generated content

💡 Proposed Solution
Make the chat container responsive to available width, so when panels
are collapsed, the conversation stretches to use the reclaimed space.

Options to consider:
1. Chat width dynamically fills the viewport minus open sidebars.
2. A toggle (e.g. "Wide mode" / "Compact mode") to force full-width reading.
3. A max-width cap for readability, adjustable in Settings.

✅ Expected Benefit
- Better readability for wide content (charts, tables, long lines of code)
- More efficient use of screen real estate on wide monitors
- More consistent experience when toggling sidebar visibility

🖥️ Environment
- Platform: Web (also noticed on desktop resolutions 1080p+)
- Reproducible: collapse both side panels → chat width stays small