Support Per-environment file-based tasks

[tmepple]

MISE_ENV already filters inline TOML tasks via mise.{env}.toml, but file-based scripts under .mise/tasks/ are always loaded regardless of environment. This makes it impossible to scope file-based tasks to specific environments (host vs devcontainer, dev vs CI, OS-specific tooling).

Of course you can disallow running certain tasks inside the wrong environments by failing and giving the user a warning but it would be nice if mise tasks ls doesn't even show the file based tasks which are not applicable to the environment you are running in.

In my case my environments are devcontainer or host (since parts of my monorepo are run in either of those two environments) but I have to think this makes sense for CI or other environments.

Rather than creating another directory tree which conflicts with namespacing (i.e. .mise/tasks/devcontainer/task.sh) I think maybe we can add an optional filter to the task's frontmatter that respects the MISE_ENV setting like:

# mise description="..."
# mise env="devcontainer"           # single env
# mise env=["devcontainer", "ci"]   # multi-env

If you think this makes sense or you have alternative feedback I could make a PR but wanted to ask first.

[risu729]

I think you can exclude the default directory if you set task_config.includes?

[tmepple]

Yes thanks for this advice -- finally had time to try it out and it works great!