Fix commit parsing and improve error handling in pull-platformplatform-changes CLI command

[tjementum]

Summary & Motivation

Fix multiple issues in the pull-platformplatform-changes CLI command on Windows:

• Commit parsing failed due to incorrect handling of new line characters. Previously, the command split Git output using Environment.NewLine, which worked on Mac but not on Windows, where Git outputs \n instead of \r\n. This has been corrected to ensure proper commit recognition across operating systems.
• Fix an issue where parsing pull request descriptions containing double quotation marks (") caused the command to exit without an error. The CLI now correctly handles these cases.
• Improve error handling by adding a proper error message when pushing changes to origin fails, providing better feedback to the user.

Additionally, fix a bug in the install command on newly installed macOS systems. Previously, the installation failed if the shell configuration files for ZSH or Bash did not exist.

Checklist

• I have added tests, or done manual regression tests
• I have updated the documentation, if necessary

[linear]

PP-322 The pull-platform-changes CLI command fails on Windows