Naming, layout and comments: descriptive full-word names, one item per line in wrapped calls and literals, and doc comments on exported names

Short and single-letter names in application code become full words (tests
keep theirs). Wrapped calls, signatures and composite literals put one item
per line, and one-line function bodies are expanded. Exported names and
groups of constants get doc comments, and comments refer to the renamed
identifiers.

internal/logging/logging.go

@@ -135,9 +135,9 @@ func (h terminalHandler) WithGroup(name string) slog.Handler {
 	}
 }
 
-// IsJSONHandler reports whether h writes JSON, as the file logger does.
-func IsJSONHandler(h slog.Handler) bool {
-	_, ok := h.(*slog.JSONHandler)
+// IsJSONHandler reports whether handler writes JSON, as the file logger does.
+func IsJSONHandler(handler slog.Handler) bool {
+	_, ok := handler.(*slog.JSONHandler)
 	return ok
 }