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/store/common.go

@@ -24,7 +24,9 @@ func OpenDB(path string) (*sql.DB, error) {
 // ErrNeedsMigration. Intended for tests and throwaway databases; applications
 // should migrate explicitly with the migrate command.
 func WithAutoMigrate() Option {
-	return func(o *options) { o.autoMigrate = true }
+	return func(opts *options) {
+		opts.autoMigrate = true
+	}
 }
 
 // dsn builds the mattn/go-sqlite3 connection string.