Embedded terminal: remove or increase scrollback history cap

Feature Request

Summary

The embedded terminal panel in the Claude Code desktop app has a maximum scrollback history limit. Once output exceeds the cap, older lines are lost and cannot be scrolled back to.

Current Behavior

The embedded terminal truncates scrollback history at a fixed cap. Output from earlier in the session is no longer accessible once the buffer fills up.

Expected Behavior

The embedded terminal should either:

1. Remove the cap entirely — keep full scrollback history for the session, like iTerm2's unlimited scrollback option.
2. Make it user-configurable — expose a setting (e.g. in settings.json) to control the scrollback buffer size, so users can raise or remove the limit based on their needs.

Why

Long-running sessions (builds, test runs, install output) regularly exceed the current cap. Losing earlier output makes debugging significantly harder — users have to re-run commands just to see output that was already produced.