fix(dbml): resolve commented cross-file // Ref: lines

Commented refs are collected per file and resolved against the combined
model after all inputs are loaded (directory, --from-list, merge, jobs).
Matched refs become FKs and relationships; duplicates of existing FKs are
skipped; missing targets are skipped with a warning; column type
mismatches warn.

Also keep reused index names within a DBML table instead of overwriting,
give a second FK to the same table a distinct relationship name, and make
the pgsql writer match relationships to FKs by name first.

cmd/relspec/templ.go

@@ -114,6 +114,7 @@ func runTempl(cmd *cobra.Command, args []string) error {
 	if err != nil {
 		return fmt.Errorf("failed to read source: %w", err)
 	}
+	finalizeCommentedRefs(db, stderrWarn)
 
 	// Print database stats
 	schemaCount := len(db.Schemas)