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/writers/gorm/writer_test.go

@@ -757,3 +757,48 @@ func TestTypeMapper_BuildGormTag_PreservesExplicitTypeModifiers(t *testing.T) {
 		t.Fatalf("type modifier appears duplicated in %q", tag)
 	}
 }
+
+// TestTypeMapper_BuildGormTag_MultipleUniqueIndexesDeterministic verifies
+// that when a column belongs to a unique constraint and more than one
+// unique index, the "uniqueIndex:" tag fragments always appear in the same
+// order across repeated calls, instead of following Go's randomized map
+// iteration order over Table.Constraints and Table.Indexes.
+func TestTypeMapper_BuildGormTag_MultipleUniqueIndexesDeterministic(t *testing.T) {
+	mapper := NewTypeMapper("")
+	table := &models.Table{
+		Name: "accounts",
+		Constraints: map[string]*models.Constraint{
+			"uq_z_accounts_email": {
+				Name:    "uq_z_accounts_email",
+				Type:    models.UniqueConstraint,
+				Columns: []string{"email"},
+			},
+		},
+		Indexes: map[string]*models.Index{
+			"idx_z_accounts_email_tenant": {
+				Name:    "idx_z_accounts_email_tenant",
+				Columns: []string{"email", "tenant_id"},
+				Unique:  true,
+			},
+			"idx_a_accounts_email_region": {
+				Name:    "idx_a_accounts_email_region",
+				Columns: []string{"email", "region_id"},
+				Unique:  true,
+			},
+		},
+	}
+	column := &models.Column{Name: "email", Type: "varchar", Length: 255, NotNull: true}
+
+	first := mapper.BuildGormTag(column, table)
+	for i := 0; i < 50; i++ {
+		got := mapper.BuildGormTag(column, table)
+		if got != first {
+			t.Fatalf("BuildGormTag() is non-deterministic across calls: %q vs %q", first, got)
+		}
+	}
+
+	wantOrder := "uniqueIndex:uq_z_accounts_email;uniqueIndex:idx_a_accounts_email_region;uniqueIndex:idx_z_accounts_email_tenant"
+	if !strings.Contains(first, wantOrder) {
+		t.Errorf("BuildGormTag() = %q, want uniqueIndex tags sorted (constraint before indexes, indexes by name): %q", first, wantOrder)
+	}
+}