Add #[track_caller] to sha256::Midstate::new()

What changed, and why it matters

This commit adds a Rust compiler annotation called #[track_caller] to a single function. It does not change what the program does, how it validates inputs, or how it handles errors. It only improves the quality of panic messages so that if the function panics, the reported error location points to the caller's code rather than inside this library function. There is no security fix here.

Security signals we found

Evidence from the diff

Changed components

diff --git a/hashes/src/sha256/mod.rs b/hashes/src/sha256/mod.rs
index 6633c673..e0fe318d 100644
--- a/hashes/src/sha256/mod.rs
+++ b/hashes/src/sha256/mod.rs
@@ -182,6 +182,7 @@ impl Midstate {
     /// # Panics
     ///
     /// Panics if `bytes_hashed` is not a multiple of 64.
+    #[track_caller]
     pub const fn new(state: [u8; 32], bytes_hashed: u64) -> Self {
         if bytes_hashed % 64 != 0 {
             panic!("bytes hashed is not a multiple of 64");