feat(pgsql): diff against the live database by default for direct output

Direct pgsql output (job output.conn_env, merge --output-conn) now reads the live
schema and executes only the differences. full_ddl: true (job option) or --full-ddl
(merge) restores the full idempotent DDL; file output is unchanged.

- compare PKs by columns, skip constraint-backed indexes, normalize index method,
  FK actions, serial/numeric types, default literals/casts and truncated names
- diff table and column comments instead of re-emitting them
- remove leftover ZZDUMP debug code

pkg/writers/pgsql/diff_statements_test.go

@@ -380,3 +380,30 @@ func TestDiffStatements_TruncatedConstraintNameMatches(t *testing.T) {
 		t.Fatalf("expected truncated live name to match, got:\n%s", diffJoin(stmts))
 	}
 }
+
+func TestColumnDefaultsEqual_LiveRepresentations(t *testing.T) {
+	tests := []struct {
+		name       string
+		model, cur interface{}
+		want       bool
+	}{
+		{"cast wrapped in parentheses", "gen_random_uuid()::text", "(gen_random_uuid())::text", true},
+		{"jsonb re-spaced array", `'["openid","profile","email"]'`, `'["openid", "profile", "email"]'::jsonb`, true},
+		{"backticked function", "`now()`", "now()", true},
+		{"quoted literal with cast", "'[]'", "'[]'::jsonb", true},
+		{"jsonb array already unquoted by the reader", `'["openid","profile"]'`, `["openid", "profile"]`, true},
+		{"text with spaces and braces", "`'{actor} #{actor_id} - {chartofaccount}'`", "{actor} #{actor_id} - {chartofaccount}", true},
+		{"cast on plain function stays equal", "gen_random_uuid()::text", "gen_random_uuid()::text", true},
+		{"different jsonb content", `'["a"]'`, `'["b"]'::jsonb`, false},
+		{"different function", "gen_random_uuid()::text", "(now())::text", false},
+		{"different literal", "'active'", "'inactive'::text", false},
+		{"nil vs value", nil, "now()", false},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := columnDefaultsEqual(tt.model, tt.cur); got != tt.want {
+				t.Errorf("columnDefaultsEqual(%v, %v) = %v, want %v", tt.model, tt.cur, got, tt.want)
+			}
+		})
+	}
+}