fix(render): unwrap BlockNote tableCell objects so table cells render content

BlockNote >=0.15 (the editor ships 0.47) stores each table cell as a
{type:"tableCell", content:[...]} object. The renderer passed each cell
straight to inlineContentFromRaw, which only understands strings and bare
inline arrays, so object-form cells rendered an empty grid (correct rows
and columns, no content). Unwrap content[] from tableCell objects while
keeping the legacy bare-array/string cell formats working.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

render/blocknote.go

@@ -374,8 +374,17 @@ func renderBlock(ctx context.Context, block map[string]any) string {
 									cellTag = "th"
 									cellClass = "px-4 py-3 text-left text-sm font-semibold"
 								}
+								// BlockNote >=0.15 wraps each cell as a tableCell object
+								// {type:"tableCell", content:[...]}; older docs store the
+								// cell's inline content (string or array) directly.
+								cellContent := cell
+								if cellMap, ok := cell.(map[string]any); ok {
+									if t, _ := cellMap["type"].(string); t == "tableCell" {
+										cellContent = cellMap["content"]
+									}
+								}
 								fmt.Fprintf(&sb, "<%s class=\"%s\">", cellTag, cellClass)
-								sb.WriteString(renderInlineContent(inlineContentFromRaw(cell), false))
+								sb.WriteString(renderInlineContent(inlineContentFromRaw(cellContent), false))
 								fmt.Fprintf(&sb, "</%s>", cellTag)
 							}
 						}

render/blocknote_test.go

@@ -520,6 +520,40 @@ func TestTableCellStringContent(t *testing.T) {
 	}
 }
 
+// BlockNote >=0.15 (the editor ships 0.47) stores each table cell as a
+// tableCell object: {type:"tableCell", props:{...}, content:[...inline]}.
+// The renderer must unwrap content[] from these objects, not just bare
+// inline arrays/strings.
+func TestTableCellObjectContent(t *testing.T) {
+	cell := func(text string) map[string]any {
+		return map[string]any{
+			"type":    "tableCell",
+			"props":   map[string]any{},
+			"content": []any{map[string]any{"type": "text", "text": text}},
+		}
+	}
+	doc := map[string]any{
+		"blocks": []any{
+			map[string]any{
+				"type": "table",
+				"content": map[string]any{
+					"type": "tableContent",
+					"rows": []any{
+						map[string]any{"cells": []any{cell("Header A"), cell("Header B")}},
+						map[string]any{"cells": []any{cell("Cell A"), cell("Cell B")}},
+					},
+				},
+			},
+		},
+	}
+	html := BlockNoteToHTML(context.Background(), doc)
+	for _, want := range []string{"Header A", "Header B", "Cell A", "Cell B"} {
+		if !strings.Contains(html, want) {
+			t.Errorf("expected table cell content %q in output: %s", want, html)
+		}
+	}
+}
+
 func TestNestedListRendering(t *testing.T) {
 	doc := map[string]any{
 		"blocks": []any{