Add .profile support on Linux for login shells and non-interactive environments

[shannah]

Summary

This PR extends the PATH management on Linux systems to include .profile in addition to .bashrc. This ensures that the PATH is properly configured for login shells, SSH sessions, cron jobs, and other non-interactive shell environments that don't source .bashrc.

Key Changes

• Linux .profile support: Modified UnixPathManager.addToPath() to write PATH exports to .profile on Linux systems, while continuing to avoid creating .bash_profile (which would break Ubuntu's convention where .profile sources .bashrc)
• Preserved macOS behavior: Maintained existing macOS logic that creates .bash_profile when neither .bash_profile nor .profile exist
• Respect opt-out mechanism: Added support for the NO_AUTO_PATH_MARKER in .profile to allow users to prevent automatic PATH modifications
• Comprehensive test coverage: Added three new test cases:
  • testAddToPathOnLinuxCreatesProfileForNonInteractiveShells: Verifies .profile is created on Linux with proper PATH export
  • testAddToPathOnLinuxRespectsNoAutoPathInProfile: Ensures the opt-out marker is respected in .profile
  • Updated existing tests to verify .profile handling in various scenarios

Implementation Details

• On Linux, .profile is now always updated (or created) alongside .bashrc and .zshrc
• The original .profile content is preserved when updating
• .bash_profile is never created on Linux to maintain compatibility with Ubuntu's shell configuration chain
• The change ensures PATH availability across all shell invocation types: interactive, login, and non-interactive shells

https://claude.ai/code/session_01Xy8SLn7cu5xwVB4NKWBiQX