fix: rayon -> tokio

[jdx]

The deadlock issue reported by many people but the cause seems related to using rayon for parallelism. This PR switches to using async rust with tokio which should resolve it.

This is obviously a massive PR so don't be surprised if there is a bug in some untested code path.

Fixes #5149
Fixes #5144
Fixes #4302
Fixes #4127

[github-actions]

If you are adding a new tool to mise, note the following:

• New asdf plugins are not accepted
• Tools may be rejected if they are not notable
• A test is required in registry.toml

[Copilot]

Pull Request Overview

This PR fully converts the CLI and backend implementations from synchronous to asynchronous execution under Tokio, replacing blocking patterns and Rayon. Key updates include:

• Changing all run, cache, and backend methods to async fn and using async_trait for the Backend trait.
• Introducing cache_async and a new get_or_try_init_async in CacheManager for asynchronous caching.
• Refactoring Ubi installation logic into an async free function and updating many backends to use .await.

Reviewed Changes

Copilot reviewed 156 out of 156 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/cli/alias/*.rs	Converted alias commands’ run to async fn and awaited config fetches
src/cache.rs	Added cache_async: OnceCell and get_or_try_init_async
src/backend/mod.rs	Annotated Backend trait with async_trait, made core methods async
src/backend/vfox.rs	Converted VfoxBackend methods to async/await
src/backend/ubi.rs	Extracted Ubi install into async helper (install), removed blocking runtime use
src/backend/external_plugin_cache.rs	Made external plugin cache methods async
Cargo.toml	Added async-trait and expanded Tokio features

Comments suppressed due to low confidence (3)

src/backend/vfox.rs:48

• VfoxBackend does not implement Clone, so calling self.clone() will not compile. Consider capturing an Arc<Self> in the async context or deriving Clone for VfoxBackend and ensuring correct ownership.

let this = self.clone();

src/backend/ubi.rs:340

• Calling block_on inside an async function can deadlock the Tokio runtime. Instead, await ubi.install_binary().await directly without using block_on.

rt.block_on(async {

src/backend/external_plugin_cache.rs:21

• The signature references Future but std::future::Future is not imported. Add use std::future::Future; or fully qualify the type to avoid compilation errors.

pub async fn list_bin_paths<F, Fut>(

[github-actions]

e2e/perf/test_many_tasks

• NUM_TASKS: 2000
• NUM_TOOLS: 200

Command	Uncached mise	Cached mise	Uncached mise-2025.5.12	Cached mise-2025.5.12
install	2171ms	198ms	510ms	182ms
ls	700ms	80ms	374ms	56ms
bin-paths	841ms	76ms	384ms	59ms
task-ls	6090ms	320ms	10006ms	10006ms