feat(cli): add select all text functionality for input

[perinst]

What does this PR do?

Feature #8504
Add Ctrl+Shift+A shortcut to select all text in the CLI input prompt. Added input_select_all keybind config and registered select-all action in textarea keybindings.

How did you verify your code works?

[github-actions]

Thanks for your contribution!

This PR doesn't have a linked issue. All PRs must reference an existing issue.

Please:

1. Open an issue describing the bug/feature (if one doesn't exist)
2. Add Fixes #<number> or Closes #<number> to this PR description

See CONTRIBUTING.md for details.

[github-actions]

The following comment was made by an LLM, it may be inaccurate:

Based on my search, I found one potentially related PR:

Related PR:

• feat(tui): add configurable readline-style text transformations #6778 - feat(tui): add configurable readline-style text transformations

This PR may be related as it addresses textarea/input keybindings and text transformations in the TUI/CLI interface. However, it appears to be focused on readline-style transformations rather than specifically select-all functionality.

The searches returned primarily PR #8503 (the current PR), indicating there are no other open PRs with the exact same select-all text functionality feature.

[github-actions]

Closing this pull request because it has had no updates for more than 60 days. If you plan to continue working on it, feel free to reopen or open a new PR.