perf(gengo): fold .NOT. <literal> at compile time

`.NOT. .T.` / `.NOT. .F.` emit PushBool directly instead of
pushing the source bool and calling Not(). boolLiteralValue also
sees through an outer NOT, so `IF !.F.` now triggers the full
dead-branch pass (no PopLogical wrapper either).

FiveSql2 43/43, Harbour compat 56/56.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

compiler/gengo/gengo.go

@@ -1265,9 +1265,17 @@ func (g *Generator) emitCallAsStmt(call *ast.CallExpr, locals localMap) {
 	g.writeln(fmt.Sprintf("t.Do(%d)", len(call.Args)))
 }
 
-// boolLiteralValue returns (value, true) if e is a bare .T./.F. literal.
-// Used by emitIf to skip dead branches.
+// boolLiteralValue returns (value, true) if e reduces to a .T./.F.
+// literal at compile time. Sees through an outer `.NOT.` so expressions
+// like `!.F.` also collapse. Used by emitIf to skip dead branches and
+// by the AND/OR short-circuit emitter.
 func boolLiteralValue(e ast.Expr) (bool, bool) {
+	if u, ok := e.(*ast.UnaryExpr); ok && u.Op == token.NOT {
+		if v, ok := boolLiteralValue(u.X); ok {
+			return !v, true
+		}
+		return false, false
+	}
 	lit, ok := e.(*ast.LiteralExpr)
 	if !ok {
 		return false, false
@@ -1988,6 +1996,17 @@ func (g *Generator) emitExpr(expr ast.Expr) {
 				}
 			}
 		}
+		// Fold `.NOT. .T.` → .F. and `.NOT. .F.` → .T. at compile time.
+		if e.Op == token.NOT {
+			if v, ok := boolLiteralValue(e.X); ok {
+				if v {
+					g.writeln("t.PushBool(false)")
+				} else {
+					g.writeln("t.PushBool(true)")
+				}
+				break
+			}
+		}
 		g.emitExpr(e.X)
 		g.emitUnaryOp(e.Op)
 	case *ast.AssignExpr: