v0.5.5: crash reports go to a dedicated CRASHLOG USB stick

The fault handler now writes crash.log to the volume labeled CRASHLOG
(label-selected via fat::crash_vol), falling back to slot 0.  On real
hardware the boot USB may be unwritable, so a second stick labeled
CRASHLOG survives the write; the shell auto-prints the previous crash
report from it at next boot (read_crash_log resolves /disk/<uid>/crash.log
through the FAT path, since Disk nodes hold no cached children).

- fat.rs: volume_label() + crash_vol() (no allocation)
- fs.rs: write_crash_log targets crash_vol(); read_crash_log prefers the
  CRASHLOG disk node; drop now-unused first_disk()
- mkdisk.sh: --label option
- test-fault.sh: boots with a dedicated CRASHLOG stick (mkfs -F 32 -n
  CRASHLOG), verifies crash.log lands there and NOT on the ESP

1 files changed, 3 insertions, 3 deletions

diff --git a/rsnix/src/gop.rs b/rsnix/src/gop.rs
index d37468f..7aeb224 100644
--- a/rsnix/src/gop.rs
+++ b/rsnix/src/gop.rs
@@ -257,7 +257,8 @@ pub fn init(gop: &mut GraphicsOutputProtocol) {
             let words = (fbinfo.pitch * fbinfo.height) / 4;
             if words > 0 {
                 let bytes = words * 4;
-                #[allow(clippy::slow_vector_initialization)] // deliberate: try_reserve must not panic
+                #[allow(clippy::slow_vector_initialization)]
+                // deliberate: try_reserve must not panic
                 let mut v: alloc::vec::Vec<u32> = alloc::vec::Vec::new();
                 if v.try_reserve_exact(words).is_ok() {
                     v.resize(words, 0); // can't fail after the reserve
@@ -284,8 +285,7 @@ pub fn init(gop: &mut GraphicsOutputProtocol) {
                     rbase + rsize,
                 );
                 if SHADOW.is_null() {
-                    let msg =
-                        "gop: WARNING — shadow rejected (fb overlap); no-shadow fallback";
+                    let msg = "gop: WARNING — shadow rejected (fb overlap); no-shadow fallback";
                     crate::serial_println!("{}", msg);
                     let lines: alloc::vec::Vec<&str> = msg
                         .as_bytes()