Restore Ctrl+R reverse command history search functionality

Current behavior: Ctrl+R toggles detailed transcript view
Requested behavior: Ctrl+R should provide reverse command history search (as documented and in previous versions)
Version: Claude Code 2.0.13

The Ctrl+R shortcut used to provide interactive command history search functionality, which was very useful for finding and reusing previous commands. This has been replaced with transcript toggling, but reverse search is a much more valuable workflow feature.

Suggested solutions:

• Restore Ctrl+R for reverse search
• Assign transcript toggle to a different shortcut
• Make keyboard shortcuts configurable
• Add alternative shortcut for reverse search

This matches the documented behavior and is a standard terminal feature users expect.