fix(codegen): sort map iteration to make generated output deterministic

Table.Columns/Constraints/Indexes/Relationships are Go maps, and every
writer, reader, diff, inspector, and merge code path that iterated them
directly was subject to Go's randomized map order, so identical input
could produce different output (or a different in-report violation/diff
order) on every run. Most visibly this showed up as bun/gorm `unique:`
struct tags changing order across consecutive `make models` runs with no
source change.

Fixed by sorting map iteration (by Sequence then Name, or alphabetically
for string-keyed maps) everywhere the order affects generated output or
first-match tie-break logic, across the bun, gorm, sqlite, dbml, drawdb,
pgsql, prisma, graphql, typeorm, drizzle, and dctx writers; the dctx,
prisma, and typeorm readers; the shared models.GetPrimaryKey/
GetForeignKeys helpers; pkg/diff, pkg/inspector, and pkg/merge; and the
TUI column/relationship pickers in pkg/ui.

pkg/readers/prisma/reader.go

@@ -820,17 +820,31 @@ func (r *Reader) createImplicitJoinTable(model1, model2 string, tableMap map[str
 	tableMap[joinTableName] = joinTable
 }
 
-// getPrimaryKeyColumn returns the primary key column of a table
+// getPrimaryKeyColumn returns the primary key column of a table. For tables
+// with a composite primary key, the column with the lowest Sequence (or,
+// failing that, the alphabetically first Name) is returned deterministically.
 func (r *Reader) getPrimaryKeyColumn(table *models.Table) *models.Column {
 	if table == nil {
 		return nil
 	}
 
+	var pk *models.Column
 	for _, col := range table.Columns {
-		if col.IsPrimaryKey {
-			return col
+		if !col.IsPrimaryKey {
+			continue
+		}
+		if pk == nil {
+			pk = col
+			continue
+		}
+		if col.Sequence > 0 && pk.Sequence > 0 {
+			if col.Sequence < pk.Sequence {
+				pk = col
+			}
+		} else if col.Name < pk.Name {
+			pk = col
 		}
 	}
 
-	return nil
+	return pk
 }