feat: add system-wide config file support

[goodtune]

Load organization-wide defaults from a system config file before user config, allowing companies to distribute shared preferences via configuration management.

Config loading order (later overrides earlier):

1. System config (organization defaults)
2. User config (personal preferences)
3. Environment variables

System config search locations:

• $WORKTRUNK_SYSTEM_CONFIG_PATH (explicit override)
• $XDG_CONFIG_DIRS directories (colon-separated)
• Linux: /etc/xdg/worktrunk/config.toml
• macOS: /Library/Application Support/worktrunk/config.toml
• Windows: %PROGRAMDATA%\worktrunk\config.toml

Uses the same format as user config. Visible in wt config show.

Prior art in other highly correlated tools:

• https://git-scm.com/docs/git-config#Documentation/git-config.txt---system
• https://code.claude.com/docs/en/settings#when-to-use-each-scope

Cleaned up version of #960.

[max-sixty]

thanks for the reformed PR

is this actually something that people want, though? I agree re the git comparison. But I don't think I've seen this much in other tools.

Could folks share some use cases where this would be helpful?

[goodtune]

Here are some examples where it would be useful in our company.

We already deploy standardised configuration to all our developer machines to configure a proxy ANTHROPIC_BASE_URL, some OpenTelemetry config, etc in our /etc/claude-code/managed-config.json.

We have begun installing worktrunk on all their machines. We want to encourage them to use it to manage their agents worktrees, but also their interactive navigation. I have a couple of immediate use cases that I would like to standardise for them.

1. most of our projects need to collect dependencies from either submodules or some other package system based off a file in the repository
   • rather than having to ask every developer to configure post-create trigger to run git submodule update --init or our-internal-tool-that-fetches-dependencies we can do this in one place.
2. we have a hierarchy we are trying to encourage to help users get more familiar with worktrees
   • setting worktree-path = "../{{ branch | sanitize }}" in /etc/xdg/worktrunk/config.toml would allow us to not have to instruct every developer to do this themselves in ~/.config/worktrunk/config.toml

Unless we have something like this, we need to ask users to copy our preferred configuration into their home directory. They don't always follow instructions to the letter, so when they try to follow along with internal guides they get confused because they missed a step.

The philosophy I think is very sound, and is echoed through specifications such as the XDG base directory standard, and tools such as pip (/etc/pip.conf), uv (/etc/uv/uv.toml), npm (/etc/npmrc), Cargo (/.cargo/config.toml), Docker (/etc/docker/daemon.json), systemd (/etc/systemd/), SSH (/etc/ssh/ssh_config), Vim (/etc/vimrc), and Ansible (/etc/ansible/ansible.cfg). This pattern exists precisely because it solves real operational problems in managed environments.

The ability to set sensible defaults system-wide while still allowing users to override them in their personal config is well-established and makes tools manageable in enterprise/team settings. Users who don't need this feature wouldn't be affected, but for organizations deploying tools at scale, it's the difference between a smooth rollout and constant support tickets.

[max-sixty]

ok, that makes a lot of sense, thanks for the thoughtful response @goodtune

let me make some small adjustments to the code, if that's OK

[goodtune]

Absolutely, please tweak as needed!

[goodtune]

Looks good, thanks for taking the time to improve it.

[max-sixty]

hi @goodtune — wdyt about those changes? lmk if you think we can make any final improvements. ty!