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, 5 deletions

diff --git a/rsnix/src/fat.rs b/rsnix/src/fat.rs
index 13d19df..335a160 100644
--- a/rsnix/src/fat.rs
+++ b/rsnix/src/fat.rs
@@ -153,11 +153,7 @@ fn is_eoc(c: u32) -> bool {
 
 fn next_cluster(c: u32) -> Result<u32, ()> {
     let n = read_fat_entry(c);
-    if is_eoc(n) {
-        Err(())
-    } else {
-        Ok(n)
-    }
+    if is_eoc(n) { Err(()) } else { Ok(n) }
 }
 
 /// Allocate a fresh cluster: mark it EOC in the FAT and zero its data.