fix(review): address feedback from reviews 2788, 2789, 2791

- Move nodeCount increment after cycle detection to avoid over-counting
  cyclic references (sonnet #2)
- Use underscores in test case names used as filenames (sonnet #3)
- Fix function comment: 'prevent silent data loss' → 'prevent confusing
  behavior where additional documents are silently ignored' (sonnet #4)
- Mark design doc pseudocode as historical since implementation uses
  goccy/go-yaml ast.Node, not gopkg.in/yaml.v3 yaml.Node (sonnet #5)

docs/DESIGN-57-yaml-persona.md

@@ -33,6 +33,11 @@ func parsePersona(data []byte, source string) (*Persona, error) {
 
 ### YAML Parsing with Depth Protection
 
+> **Note:** The pseudocode below reflects the initial design using `gopkg.in/yaml.v3`
+> types (`yaml.Node`). The actual implementation uses `github.com/goccy/go-yaml`
+> with `ast.Node`-based traversal, dual-map cycle/depth tracking, and node-count
+> limits. See `review/persona.go` for the current implementation.
+
 ```go
 func unmarshalYAMLWithDepthLimit(data []byte, out any, maxDepth int) error {
     var node yaml.Node