github actions: Update interdiff for added/deleted file diffs, file modes

Here is a complete summary written by Claude of what's changed:

New features:

- File creation/deletion diffing: When both patches add or delete the same
  file, interdiff now diffs the content of those files against each other,
  rather than skipping them. In fuzzy mode, these results appear under two
  new sections: "ADDED FILE DIFFERENCES" and "DELETED FILE DIFFERENCES".

- File mode support: interdiff now handles file permission changes in
  patches, detecting and reporting any permission differences between the
  two patches. This even works for patches that only change file
  permissions (e.g. making a file executable) with no content changes.
  Previously interdiff had no mode diffing at all.

Bug fixes:

- Hunk header parsing: Fixed a bug that could produce wrong output for any
  hunk where the before or after side is a single line (e.g. a hunk that
  deletes several lines down to one). In unified diff format, the line
  count is omitted from the hunk header when it is 1. This case was not
  being handled correctly, resulting in uninitialized stack variable usage.

- Stale temporary file cleanup: interdiff now cleans up temporary files
  that could be left behind in TMPDIR after processing. The previous
  version would also leave behind temporary files for patches that created
  or deleted a file, since it skipped those patches entirely without doing
  proper cleanup.

- Memory leak: Fixed a memory leak when processing patches that share no
  files in common.

Author: kerneltoast

.github/workflows/validate-kernel-commits.yml

@@ -189,7 +189,7 @@ jobs:
       - name: Clone and build custom patchutils
         run: |
           # Security: Pin to specific commit to prevent supply chain attacks
-          EXPECTED_COMMIT="b0090afd47557515b423e05be66494a4d5429fad"
+          EXPECTED_COMMIT="df4b62b49b4aceaecf9df7b5c4139aecf8498fa6"
 
           # Clone repository at the specific commit we want
           git clone https://github.com/kerneltoast/patchutils.git --depth=1 --revision="$EXPECTED_COMMIT"