[PR #30] tokio runtime flavor implicit — annotate multi_thread explicitly

[obchain]

PR: #30 (feat/05-clap-cli)
File: crates/charon-cli/src/main.rs
Line: ~32

Problem:

#[tokio::main]
async fn main() -> Result<()> {

multi_thread flavor is active only because workspace tokio dep carries features = ["full"]. Future compile-time features trim silently downgrades to current_thread, serializing all scanner I/O without compile error or test failure.

Fix:

#[tokio::main(flavor = "multi_thread")]
async fn main() -> Result<()> {

One annotation makes concurrency contract auditable and resilient to dep changes.

[obchain]

Fixed on feat/05-clap-cli in a235488.