GeezerVison

Summary

This change adds a typed runtime hook API to Arty.

• Add HookFn<H, D>, which keeps worker-local data and a plain function pointer together.
• Make HookFn cloneable and ThreadAware. Arty clones and relocates its data for each worker.
• Let RuntimeBuilder::on and RuntimeControl::on accept any value that converts into HookFn.
• Let third-party types implement standard From conversions without an Arty-specific adapter trait.
• Add OnStart and OnPanic hook events.
• Add OnPanic::IGNORE for the common policy that keeps the runtime running.
• Replace async panic-policy configuration with OnPanic callbacks. Shutdown remains the default action.
• Let arty_tokio::init retain private OnStart state for workers that future dynamic scaling creates.

API

use arty::runtime::Runtime;
use arty::runtime::hook::{HookFn, OnPanic, OnStart};

let runtime = Runtime::builder()
    .on(Foo::new(data))
    .on(OnPanic::IGNORE)
    .on(HookFn::<OnStart, _>::new((), |event, ()| {
        let _worker = event.thread();
    }))
    .build()?;

A third-party hook can carry its data and callback through a standard conversion:

impl From<Foo> for HookFn<OnPanic, Foo> {
    fn from(foo: Foo) -> Self {
        HookFn::new(foo, Foo::on_panic)
    }
}

Behavior

Hooks run in registration order. OnStart runs before RuntimeBuilder::build returns. Late registrations use the prioritized system-command queue for each worker. The runtime ignores registrations after shutdown starts.

Each async worker keeps one hook registry in worker-local storage. Hook invocation does not clone or move the registry or callback data.

OnPanic covers async task creation and task polling. A callback can call ignore() to keep the runtime available. It can call shutdown() to stop the runtime.

Blocking panics do not invoke OnPanic and do not stop the runtime. Their join handles still return the original panic payload.

The entry-point macros, runtime documentation, example, public contract tests, and Tokio compatibility layer use the new API.

Validation

• cargo check -p arty -p arty_executor -p arty_macros_impl -p anyspawn --all-targets
• cargo clippy -p arty --all-targets --all-features -- -D warnings
• cargo test -p arty --test runtime_hooks --test panic --test construction --test public_paths
• cargo test -p arty_executor --test lifecycle
• cargo test -p arty_macros_impl
• cargo check -p arty_tokio --all-targets
• cargo test -p arty_tokio --test compatibility
• cargo clippy -p arty_tokio --all-targets --all-features -- -D warnings
• just anvil-fmt
• just anvil-readme --fix
• cargo check -p arty --all-targets after the final HookFn cleanup