Allow disabling/remapping the "Ctrl+C twice to exit" behavio

### Describe the feature or problem you'd like to solve

Feature request: Allow disabling/remapping the "Ctrl+C twice to exit" behavior. I frequently use Ctrl+C out of habit (from other terminal tools) for two purposes: (1) cancelling an in-progress operation, and (2) copying selected text. In both cases, a second incidental Ctrl+C press exits the CLI entirely and loses my session context. This is especially disruptive since Ctrl+C for copy is a standard OS/terminal convention outside this CLI. Suggest adding a setting (e.g.,  /settings set ctrlCExit false ) to disable exit-on-double-Ctrl+C, keeping Ctrl+C available for cancel/copy, with Ctrl+D remaining as the explicit shutdown key.

### Proposed solution

_No response_

### Example prompts or workflows

_No response_

### Additional context

_No response_

Start by tracing the CLI's Ctrl+C handling and the existing settings command or configuration entry point; no specific files or tests are named in the issue. Confirm how cancellation, copy-related Ctrl+C presses, double-press exit, and Ctrl+D shutdown currently interact, then verify that the behavior can be disabled or remapped without removing the explicit shutdown path.

Written by the indexing model from the issue text.