Fix last xxd prose reference in safe-editing.md

what:
- Replace 'Verify the result with xxd' with 'Verify with od -A x -t x1z | grep 5c'
  in safe-editing.md prose

why:
The code blocks already use od instead of xxd but the prose instruction
still referenced the old Linux-only tool. The explanatory note about xxd
not being available everywhere is kept as-is — it documents why od was chosen.

Author: CodeSigils

skill/references/safe-editing.md

@@ -33,7 +33,7 @@ content = content.replace(
 write_file("/path/to/file", content)
 ```
 
-Use raw strings `r'...'` so Python doesn't process the backslashes. Verify the result with `xxd`.
+Use raw strings `r'...'` so Python doesn't process the backslashes. Verify the result with `od -A x -t x1z | grep '5c'` (see Diagnostic below).
 
 ### 2. Second Resort: `sed -i` in Single Quotes