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.

2 files changed, 13 insertions, 4 deletions

diff --git a/rsdosedit/Cargo.toml b/rsdosedit/Cargo.toml
index b271eef..92a8123 100644
--- a/rsdosedit/Cargo.toml
+++ b/rsdosedit/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rsdosedit"
 version = "0.1.0"
-edition = "2021"
+edition = "2024"
 
 [lints]
 workspace = true
diff --git a/rsdosedit/src/lib.rs b/rsdosedit/src/lib.rs
index cfb3b0e..8f67514 100644
--- a/rsdosedit/src/lib.rs
+++ b/rsdosedit/src/lib.rs
@@ -191,9 +191,15 @@ impl Editor {
 
         let help_lines = [
             ("", ""),
-            ("  \u{2550}", "\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}"),
+            (
+                "  \u{2550}",
+                "\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}",
+            ),
             ("         rsedit", " \u{2014} Keybindings"),
-            ("  \u{2550}", "\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}"),
+            (
+                "  \u{2550}",
+                "\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}\u{2550}",
+            ),
             ("", ""),
             ("  Arrow keys", "              Move cursor"),
             ("  ^\u{2190} / ^\u{2192}", "       Word backward/forward"),
@@ -208,7 +214,10 @@ impl Editor {
             ("  Tab", "                     Insert spaces (smart tab)"),
             ("  ^S", "                      Save file"),
             ("  ^W", "                      Search forward"),
-            ("  ^X", "                      Exit (twice to discard changes)"),
+            (
+                "  ^X",
+                "                      Exit (twice to discard changes)",
+            ),
             ("  ^Z", "                      Suspend editor (job control)"),
             ("  ^_", "                      Undo"),
             ("  ^G", "                      This help"),