fixup: close PR #263 review gaps

- mergeStatementAnnotations: add WhileStmt case (was falling through to
  default: nil, so @caption on a WHILE was silently dropped).
- applyAnnotations: add LoopedActivity case — LOOP and WHILE activities can
  now carry the captions they already parse.
- Add TestLoopCaptionPreserved, TestWhileLoopCaptionPreserved, and
  TestInheritanceSplitCaptionApplied to cover the gaps ako flagged (loop and
  InheritanceSplit caption paths were previously untested).
- Add `mdl-examples/bug-tests/263-nested-caption-preservation.mdl`
  reproducer per CLAUDE.md checklist.

Author: hjothamendix

mdl-examples/bug-tests/263-nested-caption-preservation.mdl

@@ -0,0 +1,45 @@
+-- ============================================================================
+-- Bug #263: Preserve decision/loop captions across nested control flow
+-- ============================================================================
+--
+-- Symptom (before fix):
+--   `@caption` on an outer IF/LOOP/WHILE was being overwritten by the inner
+--   IF/LOOP's caption because `pendingAnnotations` was shared mutable state
+--   across recursive addStatement calls. Annotations attached to the outer
+--   split ended up bound to the inner split, and the outer split inherited
+--   whatever caption the inner statement carried.
+--
+-- After fix:
+--   addIfStatement / addLoopStatement / addWhileStatement snapshot + clear
+--   `pendingAnnotations` before recursing, then re-apply to their own activity
+--   after it's created. The WHILE case also gained explicit handling in
+--   mergeStatementAnnotations (previously fell through to `default: nil`).
+--
+-- Usage:
+--   mxcli exec mdl-examples/bug-tests/263-nested-caption-preservation.mdl -p app.mpr
+--   Open in Studio Pro — each split/loop displays its own caption, not
+--   inherited from a nested statement.
+-- ============================================================================
+
+create module BugTest263;
+
+create microflow BugTest263.MF_NestedCaptions (
+  $S: string
+)
+returns boolean as $ok
+begin
+  declare $ok boolean = false;
+
+  @caption 'String not empty?'
+  if $S != empty then
+    @caption 'Right format?'
+    if isMatch($S, 'x') then
+      return true;
+    else
+      return false;
+    end if;
+  else
+    return false;
+  end if;
+end;
+/

mdl/executor/cmd_microflows_builder_annotations.go

@@ -37,6 +37,8 @@ func getStatementAnnotations(stmt ast.MicroflowStatement) *ast.ActivityAnnotatio
 		return s.Annotations
 	case *ast.LoopStmt:
 		return s.Annotations
+	case *ast.WhileStmt:
+		return s.Annotations
 	case *ast.LogStmt:
 		return s.Annotations
 	case *ast.CallMicroflowStmt:
@@ -138,6 +140,12 @@ func (fb *flowBuilder) applyAnnotations(activityID model.ID, ann *ast.ActivityAn
 				if ann.Caption != "" {
 					activity.Caption = ann.Caption
 				}
+			case *microflows.LoopedActivity:
+				// LOOP / WHILE activities can carry a caption just like
+				// splits and action activities.
+				if ann.Caption != "" {
+					activity.Caption = ann.Caption
+				}
 			}
 
 			break

mdl/executor/cmd_microflows_builder_annotations_test.go

@@ -219,3 +219,94 @@ func TestIfAnnotationStaysWithCorrectSplit(t *testing.T) {
 		t.Errorf("inner note destination: got %q, want %q (inner split)", innerNoteDestID, innerSplit.ID)
 	}
 }
+
+// TestLoopCaptionPreserved covers the loop caption case — previously untested
+// per PR review. The fix for the outer-IF caption contamination bug also applied
+// the same snapshot/restore pattern to addLoopStatement and addWhileStatement.
+func TestLoopCaptionPreserved(t *testing.T) {
+	innerReturn := &ast.ReturnStmt{Value: &ast.LiteralExpr{Value: true, Kind: ast.LiteralBoolean}}
+	loop := &ast.LoopStmt{
+		LoopVariable: "item",
+		ListVariable: "items",
+		Body:         []ast.MicroflowStatement{innerReturn},
+		Annotations:  &ast.ActivityAnnotations{Caption: "Process each item"},
+	}
+
+	fb := &flowBuilder{
+		posX:         100,
+		posY:         100,
+		spacing:      HorizontalSpacing,
+		varTypes:     map[string]string{"items": "List of MyMod.Item"},
+		declaredVars: map[string]string{"items": "List of MyMod.Item"},
+	}
+	fb.buildFlowGraph([]ast.MicroflowStatement{loop}, nil)
+
+	var loops []*microflows.LoopedActivity
+	for _, obj := range fb.objects {
+		if l, ok := obj.(*microflows.LoopedActivity); ok {
+			loops = append(loops, l)
+		}
+	}
+
+	if len(loops) != 1 {
+		t.Fatalf("expected 1 LoopedActivity, got %d", len(loops))
+	}
+	if loops[0].Caption != "Process each item" {
+		t.Errorf("loop caption: got %q, want %q", loops[0].Caption, "Process each item")
+	}
+}
+
+// TestWhileLoopCaptionPreserved — same coverage for the WHILE shape.
+func TestWhileLoopCaptionPreserved(t *testing.T) {
+	whileStmt := &ast.WhileStmt{
+		Condition: &ast.BinaryExpr{
+			Left:     &ast.VariableExpr{Name: "n"},
+			Operator: "<",
+			Right:    &ast.LiteralExpr{Value: int64(10), Kind: ast.LiteralInteger},
+		},
+		Body: []ast.MicroflowStatement{
+			&ast.ReturnStmt{Value: &ast.LiteralExpr{Value: true, Kind: ast.LiteralBoolean}},
+		},
+		Annotations: &ast.ActivityAnnotations{Caption: "Until n >= 10"},
+	}
+
+	fb := &flowBuilder{
+		posX:         100,
+		posY:         100,
+		spacing:      HorizontalSpacing,
+		varTypes:     map[string]string{"n": "Integer"},
+		declaredVars: map[string]string{"n": "Integer"},
+	}
+	fb.buildFlowGraph([]ast.MicroflowStatement{whileStmt}, nil)
+
+	var loops []*microflows.LoopedActivity
+	for _, obj := range fb.objects {
+		if l, ok := obj.(*microflows.LoopedActivity); ok {
+			loops = append(loops, l)
+		}
+	}
+
+	if len(loops) != 1 {
+		t.Fatalf("expected 1 LoopedActivity (WHILE), got %d", len(loops))
+	}
+	if loops[0].Caption != "Until n >= 10" {
+		t.Errorf("while caption: got %q, want %q", loops[0].Caption, "Until n >= 10")
+	}
+}
+
+// TestInheritanceSplitCaptionApplied — InheritanceSplit is not produced by the
+// executor builder (only parsed from BSON for roundtrip), but applyAnnotations
+// gained an InheritanceSplit case in the fix. Test the applicator directly.
+func TestInheritanceSplitCaptionApplied(t *testing.T) {
+	split := &microflows.InheritanceSplit{}
+	split.ID = "inh-split-1"
+
+	fb := &flowBuilder{}
+	fb.objects = append(fb.objects, split)
+
+	fb.applyAnnotations(split.ID, &ast.ActivityAnnotations{Caption: "Customer type?"})
+
+	if split.Caption != "Customer type?" {
+		t.Errorf("inheritance split caption: got %q, want %q", split.Caption, "Customer type?")
+	}
+}