Allow adjusting font size of the chat/conversation panel independently from the editor

Body:

Is your feature request related to a problem? Please describe.
The Claude Code VS Code extension's chat/conversation panel shares font size with the rest of the editor. I have editor.fontSize set to a comfortable size for reading/writing code, but the same size feels too small for reading conversation text in the Claude Code panel. Currently there's no way to change one without affecting the other.

Describe the solution you'd like
A dedicated setting (e.g. claude-code.fontSize or claude-code.chat.fontSize) that controls only the text size inside the Claude Code chat panel, independent of editor.fontSize and window.zoomLevel.

Describe alternatives you've considered

• window.zoomLevel — works, but zooms the entire VS Code window, including the code editor, which I don't want.
• Per-webview zoom (Cmd+= / Ctrl+= with focus on the panel) — does not appear to work for this panel.
• OS-level display scaling — affects everything, not just this panel.

None of these let me increase only the chat panel's font size.

Additional context
This would be especially helpful for readability/accessibility when reading longer Claude responses, without having to zoom the whole editor (which makes code lines wrap awkwardly).