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/diff/diff_test.go

@@ -1,6 +1,7 @@
 package diff
 
 import (
+	"reflect"
 	"testing"
 
 	"git.warky.dev/wdevs/relspecgo/pkg/models"
@@ -140,6 +141,46 @@ func TestCompareColumns(t *testing.T) {
 	}
 }
 
+// TestCompareColumns_Deterministic verifies that Missing/Extra entries are
+// always reported in the same (alphabetical) order across repeated calls,
+// instead of following Go's randomized map iteration order over the
+// source/target column maps.
+func TestCompareColumns_Deterministic(t *testing.T) {
+	source := map[string]*models.Column{
+		"zeta":  {Name: "zeta", Type: "text"},
+		"alpha": {Name: "alpha", Type: "text"},
+		"mu":    {Name: "mu", Type: "text"},
+	}
+	target := map[string]*models.Column{
+		"omega":   {Name: "omega", Type: "text"},
+		"delta":   {Name: "delta", Type: "text"},
+		"charlie": {Name: "charlie", Type: "text"},
+	}
+
+	wantMissing := []string{"alpha", "mu", "zeta"}
+	wantExtra := []string{"charlie", "delta", "omega"}
+
+	for i := 0; i < 25; i++ {
+		got := compareColumns(source, target)
+
+		gotMissing := make([]string, len(got.Missing))
+		for j, c := range got.Missing {
+			gotMissing[j] = c.Name
+		}
+		gotExtra := make([]string, len(got.Extra))
+		for j, c := range got.Extra {
+			gotExtra[j] = c.Name
+		}
+
+		if !reflect.DeepEqual(gotMissing, wantMissing) {
+			t.Fatalf("compareColumns() Missing = %v, want %v (run %d)", gotMissing, wantMissing, i)
+		}
+		if !reflect.DeepEqual(gotExtra, wantExtra) {
+			t.Fatalf("compareColumns() Extra = %v, want %v (run %d)", gotExtra, wantExtra, i)
+		}
+	}
+}
+
 func TestCompareColumnDetails(t *testing.T) {
 	tests := []struct {
 		name   string