refactor: extract shared hash_content into execute/hash.rs (#282)

## Summary

Extract the 8 KiB buffered xxHash3_64 hashing logic from
`fingerprint.rs` and `glob_inputs.rs` into a shared `execute/hash.rs`
module.

> [!NOTE]
> I used Claude to find this duplication, reasoned with it
back-and-forth to see if it was really an improvement, concluded that it
was just a small one.
> 
> Both call sites were identical, but strictly speaking the logic
doesn't need to be shared. If not desired, just close the PR.

## Test plan
- [x] `cargo test -p vite_task` — all 27 tests pass

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
Co-authored-by: branchseer <3612422+branchseer@users.noreply.github.com>

Author: 3 people

crates/vite_task/src/session/execute/fingerprint.rs

@@ -6,8 +6,7 @@
 use std::{
     collections::BTreeMap,
     fs::File,
-    hash::Hasher as _,
-    io::{self, BufRead, Read},
+    io::{self, BufRead},
     sync::Arc,
 };
 
@@ -182,20 +181,6 @@ fn determine_folder_change_kind<'a>(
     }
 }
 
-/// Hash file content using `xxHash3_64`
-fn hash_content(mut stream: impl Read) -> io::Result<u64> {
-    let mut hasher = twox_hash::XxHash3_64::default();
-    let mut buf = [0u8; 8192];
-    loop {
-        let n = stream.read(&mut buf)?;
-        if n == 0 {
-            break;
-        }
-        hasher.write(&buf[..n]);
-    }
-    Ok(hasher.finish())
-}
-
 /// Check if a directory entry should be ignored in fingerprinting
 fn should_ignore_entry(name: &[u8]) -> bool {
     matches!(name, b"." | b".." | b".DS_Store") || name.eq_ignore_ascii_case(b"dist")
@@ -251,7 +236,7 @@ pub fn fingerprint_path(
             return process_directory(std_path, path_read);
         }
     }
-    Ok(PathFingerprint::FileContentHash(hash_content(reader)?))
+    Ok(PathFingerprint::FileContentHash(super::hash::hash_content(reader)?))
 }
 
 /// Process a directory on Windows using `std::fs::read_dir`

crates/vite_task/src/session/execute/glob_inputs.rs

@@ -5,12 +5,7 @@
 //!
 //! All glob patterns are workspace-root-relative (resolved at task graph stage).
 
-use std::{
-    collections::BTreeMap,
-    fs::File,
-    hash::Hasher as _,
-    io::{self, Read},
-};
+use std::{collections::BTreeMap, fs::File, io};
 
 #[cfg(test)]
 use vite_path::AbsolutePathBuf;
@@ -114,21 +109,9 @@ pub fn compute_globbed_inputs(
     Ok(result)
 }
 
-/// Hash file content using `xxHash3_64`.
 #[expect(clippy::disallowed_types, reason = "receives std::path::Path from wax glob walker")]
 fn hash_file_content(path: &std::path::Path) -> io::Result<u64> {
-    let file = File::open(path)?;
-    let mut reader = io::BufReader::new(file);
-    let mut hasher = twox_hash::XxHash3_64::default();
-    let mut buf = [0u8; 8192];
-    loop {
-        let n = reader.read(&mut buf)?;
-        if n == 0 {
-            break;
-        }
-        hasher.write(&buf[..n]);
-    }
-    Ok(hasher.finish())
+    super::hash::hash_content(io::BufReader::new(File::open(path)?))
 }
 
 #[cfg(test)]

crates/vite_task/src/session/execute/hash.rs

@@ -0,0 +1,15 @@
+use std::{hash::Hasher as _, io};
+
+/// Hash content using 8 KiB buffered `xxHash3_64`.
+pub(super) fn hash_content(mut stream: impl io::Read) -> io::Result<u64> {
+    let mut hasher = twox_hash::XxHash3_64::default();
+    let mut buf = [0u8; 8192];
+    loop {
+        let n = stream.read(&mut buf)?;
+        if n == 0 {
+            break;
+        }
+        hasher.write(&buf[..n]);
+    }
+    Ok(hasher.finish())
+}

crates/vite_task/src/session/execute/mod.rs

@@ -1,5 +1,6 @@
 pub mod fingerprint;
 pub mod glob_inputs;
+mod hash;
 pub mod spawn;
 
 use std::{collections::BTreeMap, io::Write as _, process::Stdio, sync::Arc};