Clean up warnings, fix FAT32 multi-cluster dirs, prep for edition 2024

Warning cleanup (cargo check + clippy now 0 across the workspace):
- Migrate all 21 static_mut_refs sites to &raw mut accessors (fat, gop,
  ps2, vt, ahci, interrupts, memory) so edition 2024 won't deny them
- panic = "abort" profiles: bare cargo check/build now works without
  nightly/-Zbuild-std
- Wire TICKS in the timer ISR (it was never incremented, so the vt scroll
  batching trigger was dead code)
- Clippy: efi_main becomes unsafe extern "efiapi" with a # Safety doc,
  KeyBuf::new uses inline-const array repeat (no interior-mutable const),
  editor main loop is a while-let, PIT control byte regrouped
- [workspace.lints.clippy] allows result_unit_err + needless_range_loop
  (deliberate kernel style); large_enum_variant allowed on LineInput
- Drop now-stale static_mut_refs allow from the rsdos bin

FAT32 correctness fixes (both pre-existing, exposed by the SFN fix):
- Unique 8.3 short names: to_8_3() never disambiguated collisions, so
  files sharing a long-name prefix got identical SFNs and fsck reported
  duplicate directory entries.  Add dir_short_names() + unique_short_name()
  (~N tails, Windows-style) and force LFN when the SFN changes.
- Multi-cluster directories: scan_dir/dir_short_names stopped at the first
  0x00 slot, hiding every entry written into a chained cluster (writes
  failed with 'cannot write', duplicate SFNs accumulated); add_dir_entry
  now packs the cluster (0xE5 deleted-markers) before extending so other
  FAT readers (mtools, Windows) see the continuation too.

Other: delete dead fields (Disk.fis, Volume.fat_count), drop timer_irq/
keyboard_irq/rendered, refresh_and_exit is a documented unsafe fn, CONTEXT
.md corrected (stable toolchain, IRQ input, 4-crate layout), .gitignore
excludes .pi-subagents artifacts.

Validated: cargo check/clippy/fmt clean, make test-disk PASS on fresh and
reused images (incl. two directory-chain extensions and ~10 SFN tails),
editor round-trip smoke test PASS.

1 files changed, 8 insertions, 3 deletions

diff --git a/rsnix/src/memory.rs b/rsnix/src/memory.rs
index c80edab..54ff7be 100644
--- a/rsnix/src/memory.rs
+++ b/rsnix/src/memory.rs
@@ -289,7 +289,7 @@ pub fn capture_memory_map(bs: &BootServices) -> Result<usize, Status> {
     let buf_size = buf_size.div_ceil(desc_size) * desc_size;
 
     // If our static buffer is too small, fall back to pool (rare)
-    if buf_size > unsafe { MAP_WORK_BUF.len() } {
+    if buf_size > unsafe { (*core::ptr::addr_of!(MAP_WORK_BUF)).len() } {
         return Err(EFI_BUFFER_TOO_SMALL);
     }
 
@@ -337,7 +337,12 @@ pub fn capture_memory_map(bs: &BootServices) -> Result<usize, Status> {
 }
 
 /// Retry ExitBootServices with a fresh memory map.
-pub fn refresh_and_exit(bs: &BootServices, image_handle: Handle) -> Result<usize, Status> {
+///
+/// # Safety
+///
+/// `image_handle` must be the valid EFI image handle this kernel was
+/// started with (opaque firmware pointer; never dereferenced here).
+pub unsafe fn refresh_and_exit(bs: &BootServices, image_handle: Handle) -> Result<usize, Status> {
     let key = capture_memory_map(bs)?;
     let status = unsafe { (bs.exit_boot_services)(image_handle, key) };
     if status == EFI_SUCCESS {
@@ -591,7 +596,7 @@ pub fn init_page_allocator() -> bool {
 
         // The bitmap itself lives in the heap (one allocation, never freed).
         // `bytes` >= 1 and align 16 is a power of two, so this cannot fail.
-        let layout = unsafe { Layout::from_size_align_unchecked(bytes, 16) };
+        let layout = Layout::from_size_align_unchecked(bytes, 16);
         let bm = ALLOCATOR.alloc(layout);
         if bm.is_null() {
             return false;