WSL / Linux support

[1shooperman]

Problem

claudenv currently targets macOS (zsh/bash). WSL (Windows Subsystem for Linux) and native Linux users use bash by default and may have different shell profile locations.

Scope

• WSL / Linux (bash): install.sh should reliably detect and write to ~/.bashrc (or ~/.bash_profile where appropriate). The core claudenv.sh function should already work — needs validation.
• Windows (native): PowerShell and cmd.exe are out of scope until someone champions them. A PowerShell port would need a separate claudenv.ps1.

Acceptance criteria

• install.sh correctly targets the right rc file on Debian/Ubuntu WSL
• claudenv activate/deactivate works in a bash session on Linux
• Prompt prefix works in bash (direct PS1 path, not the oh-my-zsh hook)
• CI or test notes updated to cover Linux

Notes

• The find ... -exec basename {} \; approach in claudenv.sh uses macOS-compatible find; verify it works with GNU find on Linux (it should)
• Process substitution < <(...) requires bash 3.2+ or zsh; verify on older Ubuntu LTS bash versions