Bump workspace to edition 2024

- edition = "2024" in the workspace manifest and rsdosedit
- extern blocks must be unsafe: interrupts.rs ISR stubs -> unsafe extern "C"
- #[no_mangle] -> #[unsafe(no_mangle)] (efi_main, isr_dispatch)
- One missed static-mut read in free_list_insert wrapped in an explicit
  unsafe block (edition 2024 removed the implicit unsafe context inside
  unsafe fns)
- rustfmt reflows for 2024: nested if-lets become let-chains, imports
  re-sorted, rsdosedit help-screen box rows wrapped

No codegen-affecting changes. Validated: cargo check/clippy/fmt clean
(host + uefi target), make test-disk PASS, editor round-trip PASS.

1 files changed, 1 insertions, 1 deletions

diff --git a/Cargo.toml b/Cargo.toml
index 0cc785d..eb42b42 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,7 @@ members = ["rsnix", "shell", "rsdos", "rsdosedit"]
 
 [workspace.package]
 version = "0.2.0"
-edition = "2021"
+edition = "2024"
 
 # no_std UEFI kernel: no unwinder available, so panic must abort.
 # (Also makes bare `cargo check`/`cargo build` without --target work.)