jj: pick a different log node format

For whatever reason, the diamond isn't rendering correctly in about
half the terminal emulators I use, and it's slowly driving me nuts, so
let's switch it up

jj/conf.d/default.toml

···
 
 [templates]
 git_push_bookmark = '"bmps/push-" ++ change_id.short()'
+log_node = '''
+coalesce(
+  if(!self, label("elided", "~")),
+  label(
+    separate(" ",
+      if(current_working_copy, "working_copy"),
+      if(immutable, "immutable"),
+      if(conflict, "conflict"),
+    ),
+    coalesce(
+      if(current_working_copy, "@"),
+      if(immutable, "●"),
+      if(conflict, "×"),
+      "○",
+    )
+  )
+)
+'''