v0.12.0: Rust 2024 edition migration

- edition = "2024" bump.
- FFI block in src/scsi/macos.rs wrapped in `unsafe extern "C" { }`.
- vtable_fn body gets an explicit unsafe block (unsafe_op_in_unsafe_fn).
- Match-ergonomics cleanup in mux/meta.rs, mkvstream.rs, network.rs,
  stdio.rs — removed redundant `ref` / `ref mut` bindings.

MSRV unchanged at 1.86. 226 tests pass. No behavior change.

src/mux/meta.rs

@@ -211,7 +211,7 @@ impl M2tsMeta {
             .iter()
             .map(|s| {
                 if let MetaStream::Video {
-                    codec_private: Some(ref b64),
+                    codec_private: Some(b64),
                     ..
                 } = s
                 {

src/mux/mkvstream.rs

@@ -150,9 +150,9 @@ impl crate::pes::Stream for MkvStream {
 
     fn write(&mut self, frame: &crate::pes::PesFrame) -> io::Result<()> {
         match &mut self.mode {
-            Mode::Write {
-                muxer: Some(ref mut m),
-            } => m.write_frame(frame.track, frame.pts, frame.keyframe, &frame.data),
+            Mode::Write { muxer: Some(m) } => {
+                m.write_frame(frame.track, frame.pts, frame.keyframe, &frame.data)
+            }
             Mode::Write { muxer: None } => Ok(()),
             Mode::Read(_) => Err(crate::error::Error::StreamReadOnly.into()),
         }

src/mux/network.rs

@@ -81,7 +81,7 @@ impl crate::pes::Stream for NetworkStream {
         match &mut self.mode {
             Mode::Write {
                 writer,
-                ref mut header_written,
+                header_written,
                 ..
             } => {
                 if !*header_written {

src/mux/stdio.rs

@@ -70,7 +70,7 @@ impl crate::pes::Stream for StdioStream {
     }
     fn write(&mut self, frame: &crate::pes::PesFrame) -> io::Result<()> {
         match &mut self.writer {
-            Some(ref mut w) => {
+            Some(w) => {
                 if !self.header_written {
                     if !self.disc_title.streams.is_empty() {
                         let m = meta::M2tsMeta::from_title(&self.disc_title);

src/scsi/macos.rs

@@ -63,7 +63,8 @@ struct SCSITaskSGElement {
 
 // ── External IOKit / CoreFoundation functions ───────────────────────────────
 
-extern "C" {
+// Rust 2024: FFI blocks declaring extern fns must be `unsafe extern`.
+unsafe extern "C" {
     fn IOMasterPort(bootstrap: u32, master: *mut MachPort) -> IOReturn;
     fn IOBSDNameMatching(
         master: MachPort,
@@ -97,10 +98,18 @@ extern "C" {
 // IOSCSIArchitectureModelFamily/UserClientLib/SCSITaskLib.h
 
 /// Read a function pointer from a COM vtable at the given index.
+///
+/// # Safety
+/// `iface` must be a valid COM interface pointer (*mut *mut c_void), and
+/// `index` must be a valid vtable slot for the target type `T`.
 unsafe fn vtable_fn<T>(iface: ComRef, index: usize) -> T {
-    let vtable = *iface as *const *const std::ffi::c_void;
-    let fn_ptr = *vtable.add(index);
-    std::mem::transmute_copy(&fn_ptr)
+    // Rust 2024: `unsafe fn` bodies are no longer implicitly unsafe.
+    // Each unsafe op needs its own `unsafe { }` block.
+    unsafe {
+        let vtable = *iface as *const *const std::ffi::c_void;
+        let fn_ptr = *vtable.add(index);
+        std::mem::transmute_copy(&fn_ptr)
+    }
 }
 
 /// Call Release (vtable index 3) on any COM interface.