fix(tui): resolve keybind conflicts and missing defaults

[google-labs-jules]

Addresses Issue anomalyco#4997 by updating default keybinding configurations and enhancing the Prompt component to handle Copy operations intelligently.

Key Changes:

1. Config Updates:
   • input_copy: Added default mapping (ctrl+c, super+c).
   • model_provider_list: Changed from ctrl+a to ctrl+alt+m to free up ctrl+a for "Line Start".
   • input_move_up/down: Added ctrl+p / ctrl+n.
   • history_previous/next: Added ctrl+p / ctrl+n.
   • input_newline: Verified shift+return.
   • input_word_forward/backward: Verified/Added ctrl+right/ctrl+left.
2. Logic Updates:
   • Prompt component now intercepts input_copy (Ctrl+C). If a text selection exists, it copies to clipboard and stops propagation. Otherwise, it allows fallback to input_clear or app_exit.

Verified via test/config_defaults.test.ts.

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PR created automatically by Jules for task 18063428155983604517 started by @Ashwinhegde19

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