git: delta uses the ansi syntax theme

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

common/git/config

@@ -15,6 +15,7 @@
 [delta]
     navigate = true      # n/N jump between files
     line-numbers = true
+    syntax-theme = ansi  # use the terminal palette
 [merge]
     conflictStyle = zdiff3
 # Structural diffs via difftastic, on demand; delta stays the default pager.