🤖 feat: add ~/.mux/bashrc for shell environment customization

[ammar-agent]

Summary

When mux launches from Applications (not terminal), agent bash commands get a minimal PATH (/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin) missing user tools like Homebrew, nix, direnv, pyenv, etc.

The standard ~/.bashrc isn't sourced because:

1. bash -c creates a non-interactive shell
2. Most bashrc files have [[ $- != *i* ]] && return guards that skip content

Solution

Add a dedicated ~/.mux/bashrc file that is always sourced before every bash command, following the existing pattern of:

• ~/.mux/AGENTS.md — global agent instructions
• <project>/.mux/init — project initialization hooks

Use Cases

# ~/.mux/bashrc

# Nix + direnv (auto-loads .envrc per workspace)
if [ -e "$HOME/.nix-profile/etc/profile.d/nix.sh" ]; then
  . "$HOME/.nix-profile/etc/profile.d/nix.sh"
fi
eval "$(direnv hook bash)"

# Homebrew (macOS)
eval "$(/opt/homebrew/bin/brew shellenv)"

# Or any version manager: pyenv, rbenv, nvm, asdf

Implementation

• LocalRuntime.exec() prepends bashrc sourcing to all commands
• SSHRuntime.exec() prepends bashrc sourcing (uses remote ~/.mux/bashrc)
• Init hooks also source bashrc for consistency
• Silently skipped if file doesn't exist

Testing

• Unit tests for the bashrc snippet
• Integration test that verifies env vars from bashrc are available

Fixes #797

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Generated with mux

[chatgpt-codex-connector]

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[tko]

Clever. I can see this can potentially make all kinds of things convenient if it works.

[tko]

direnv hook bash sets PROMPT_COMMAND which I believe means that direnv will not be activated until bash prompt is shown, which is never when running commands with bash -c

Assuming bashrc is sourced from the project directory with .envrc file then I guess running direnv export bash instead might work better (it's what direnv hook seems to run.)