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

ingestion/internal/api/handler_test.go

@@ -79,6 +79,27 @@ func TestQuery_RequiresQuery(t *testing.T) {
 	assert.Equal(t, http.StatusBadRequest, rec.Code)
 }
 
+func TestWrite_IncludesFrontmatterWhenTypeProvided(t *testing.T) {
+	dir, h := setup(t)
+	body, _ := json.Marshal(map[string]any{
+		"content":  "Some learning.",
+		"filename": "typed-note.md",
+		"type":     "concept",
+		"domain":   "software",
+	})
+	req := httptest.NewRequest(http.MethodPost, "/write", bytes.NewReader(body))
+	rec := httptest.NewRecorder()
+
+	h.Write(rec, req)
+
+	assert.Equal(t, http.StatusOK, rec.Code)
+	content, err := os.ReadFile(filepath.Join(dir, "raw", "typed-note.md"))
+	require.NoError(t, err)
+	assert.Contains(t, string(content), "type: concept")
+	assert.Contains(t, string(content), "domain: software")
+	assert.Contains(t, string(content), "Some learning.")
+}
+
 func TestWrite_GeneratesFilenameIfAbsent(t *testing.T) {
 	dir, h := setup(t)
 	body, _ := json.Marshal(map[string]any{"content": "auto name"})