fix(ingestion): preserve type and domain metadata as frontmatter in written notes

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

ingestion/internal/api/handler.go

@@ -33,6 +33,8 @@ type queryRequest struct {
 type writeRequest struct {
 	Content  string `json:"content"`
 	Filename string `json:"filename,omitempty"`
+	Type     string `json:"type,omitempty"`
+	Domain   string `json:"domain,omitempty"`
 }
 
 // Query handles POST /query — full-text search across the brain wiki.
@@ -83,8 +85,22 @@ func (h *Handler) Write(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	finalContent := req.Content
+	if req.Type != "" || req.Domain != "" {
+		var fm strings.Builder
+		fm.WriteString("---\n")
+		if req.Type != "" {
+			fmt.Fprintf(&fm, "type: %s\n", req.Type)
+		}
+		if req.Domain != "" {
+			fmt.Fprintf(&fm, "domain: %s\n", req.Domain)
+		}
+		fm.WriteString("---\n")
+		finalContent = fm.String() + req.Content
+	}
+
 	dest := filepath.Join(rawDir, filepath.Base(filename))
-	if err := os.WriteFile(dest, []byte(req.Content), 0o644); err != nil {
+	if err := os.WriteFile(dest, []byte(finalContent), 0o644); err != nil {
 		h.logger.Error("write failed", "err", err)
 		http.Error(w, "write error", http.StatusInternalServerError)
 		return