fix(examples/rich): use only constructors allowed in bot rich messages

The showcase used Instant-View-page-only page blocks (Title, Subtitle,
Header, Subheader, Kicker, AuthorDate, Cover, RelatedArticles) and the
auto-link inline styles (AutoURL/AutoEmail/AutoPhone). The Bot API server
rejects these in a bot-sent rich message with RICH_VALIDATE_CTOR_NOT_ALLOWED.

Per telegram-bot-api td/td/telegram/WebPageBlock.cpp (blocks whose
get_input_page_block logs an error are invalid input) and Client.cpp's
richText switch, drop the disallowed constructors and keep only the allowed
ones. Document the allowlist in the example doc comment and CHANGELOG.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: ernado

CHANGELOG.md

@@ -20,7 +20,10 @@ messages follow [Conventional Commits](https://www.conventionalcommits.org/).
 - **Rich messages** (Bot API 10.1) — `SendRichMessage`/`SendRichHTML`/
   `SendRichMarkdown` send structured page-block content built with
   `github.com/gotd/td/telegram/message/rich`. The `examples/rich` bot showcases
-  every page-block and rich-text constructor.
+  the page-block and rich-text constructors valid in a bot-sent message.
+  (Instant-View-page-only blocks — Title, Subtitle, Header, Subheader, Kicker,
+  AuthorDate, Cover, RelatedArticles — and the auto-link inline styles are
+  rejected by the server with `RICH_VALIDATE_CTOR_NOT_ALLOWED`.)
 - **Background sends** — `Bot.Background()` / `Context.Background()` expose a
   run-lifetime context for proactive sends to any chat from timers, queues or
   goroutines, instead of the per-update handler context. Plus `Bot.Logger()`.

examples/rich/main.go

@@ -1,15 +1,22 @@
 // Command rich is a showcase of Telegram rich messages (Bot API 10.1) built with
 // github.com/gotd/td/telegram/message/rich. Each command sends a rich message
-// exercising a category of the rich-text and page-block constructors:
+// exercising a category of the allowed rich-text and page-block constructors:
 //
-//	/headings  titles, headers, headings 1-6, kicker, author/date, footer
-//	/text      every inline text style (bold, italic, spoiler, math, links, …)
+//	/headings  headings 1-6 and a footer
+//	/text      every allowed inline text style (bold, italic, spoiler, math, …)
 //	/lists     bullet, checklist and ordered lists (incl. block items)
-//	/blocks    paragraph, preformatted, quotes, details, math, divider, anchor
+//	/blocks    paragraph, anchor, code, quotes, math, details, thinking, divider
 //	/table     a table with header and data cells
 //	/map       a map block
-//	/media     photo/audio/image/custom-emoji/cover/collage/slideshow/related
-//	           (the media-by-id blocks need real ids — see the env vars below)
+//	/media     photo/audio/image/custom-emoji/collage/slideshow (need real ids)
+//
+// Not every page block is valid in a bot-sent rich message. Per the official Bot
+// API server (telegram-bot-api, td/td/telegram/WebPageBlock.cpp), these are
+// Instant-View-page-only and the server rejects them with
+// RICH_VALIDATE_CTOR_NOT_ALLOWED, so they are intentionally not used here:
+// Title, Subtitle, Header, Subheader, Kicker, AuthorDate, Cover,
+// RelatedArticles — and the inline auto-link styles (AutoURL/AutoEmail/
+// AutoPhone). Video is omitted too.
 //
 // Run it with an MTProto app identity (https://my.telegram.org) and a BotFather
 // token. To exercise /media's media-by-id blocks, also set any of PHOTO_ID,
@@ -55,7 +62,7 @@ func main() {
 
 	bot.OnCommand("start", "List the rich-message demos", func(c *botapi.Context) error {
 		return send(c,
-			rich.Title(rich.Plain("Rich message showcase")),
+			rich.Heading1(rich.Plain("Rich message showcase")),
 			rich.Paragraph(rich.Plain("Try these commands to see the page-block constructors:")),
 			rich.List(
 				rich.ListItem(rich.Fixed(rich.Plain("/headings"))),
@@ -69,14 +76,8 @@ func main() {
 		)
 	})
 
-	bot.OnCommand("headings", "Titles and headings", func(c *botapi.Context) error {
+	bot.OnCommand("headings", "Headings and a footer", func(c *botapi.Context) error {
 		return send(c,
-			rich.Kicker(rich.Plain("KICKER")),
-			rich.Title(rich.Plain("The Title")),
-			rich.Subtitle(rich.Plain("The subtitle")),
-			rich.AuthorDate(rich.Plain("by Ada"), int(time.Now().Unix())),
-			rich.Header(rich.Plain("A header")),
-			rich.Subheader(rich.Plain("A subheader")),
 			rich.Heading1(rich.Plain("Heading 1")),
 			rich.Heading2(rich.Plain("Heading 2")),
 			rich.Heading3(rich.Plain("Heading 3")),
@@ -88,7 +89,7 @@ func main() {
 		)
 	})
 
-	bot.OnCommand("text", "Every inline text style", func(c *botapi.Context) error {
+	bot.OnCommand("text", "Every allowed inline text style", func(c *botapi.Context) error {
 		return send(c,
 			rich.Paragraph(rich.Concat(
 				rich.Bold(rich.Plain("bold")), sp(), rich.Italic(rich.Plain("italic")), sp(),
@@ -115,12 +116,6 @@ func main() {
 				rich.URL(rich.Plain("gotd/td"), "https://github.com/gotd/td", 0), sp(),
 				rich.AnchorLink(rich.Plain("jump to anchor"), "more"),
 			)),
-			rich.Paragraph(rich.Concat(
-				rich.Plain("auto-detected: "),
-				rich.AutoURL(rich.Plain("https://telegram.org")), sp(),
-				rich.AutoEmail(rich.Plain("team@telegram.org")), sp(),
-				rich.AutoPhone(rich.Plain("+15550100")),
-			)),
 			rich.Paragraph(rich.Concat(
 				rich.Plain("date: "),
 				rich.Date(rich.Plain("now"), int(time.Now().Unix()), rich.DateFlags{LongDate: true, ShortTime: true}),
@@ -131,7 +126,7 @@ func main() {
 
 	bot.OnCommand("lists", "Bullet, checklist and ordered lists", func(c *botapi.Context) error {
 		return send(c,
-			rich.Header(rich.Plain("Unordered")),
+			rich.Heading3(rich.Plain("Unordered")),
 			rich.List(
 				rich.ListItem(rich.Plain("a plain item")),
 				rich.CheckListItem(true, rich.Plain("a checked item")),
@@ -141,7 +136,7 @@ func main() {
 					rich.Preformatted(rich.Plain("nested := true"), "go"),
 				),
 			),
-			rich.Header(rich.Plain("Ordered")),
+			rich.Heading3(rich.Plain("Ordered")),
 			rich.OrderedList(
 				rich.OrderedListItem("1.", rich.Plain("first")),
 				rich.OrderedListItem("2.", rich.Plain("second")),
@@ -150,7 +145,7 @@ func main() {
 		)
 	})
 
-	bot.OnCommand("blocks", "Paragraphs, quotes, code, details, math", func(c *botapi.Context) error {
+	bot.OnCommand("blocks", "Anchor, code, quotes, math, details, divider", func(c *botapi.Context) error {
 		return send(c,
 			rich.AnchorBlock("more"),
 			rich.Paragraph(rich.Concat(
@@ -213,7 +208,6 @@ func mediaBlocks() []tg.PageBlockClass {
 	if id := envID("PHOTO_ID"); id != 0 {
 		blocks = append(blocks,
 			rich.Photo(id, caption("A photo")),
-			rich.Cover(rich.Photo(id, caption("A cover"))),
 			rich.Collage(caption("A collage"),
 				rich.Photo(id, emptyCaption()), rich.Photo(id, emptyCaption())),
 			rich.Slideshow(caption("A slideshow"),
@@ -234,11 +228,8 @@ func mediaBlocks() []tg.PageBlockClass {
 		)))
 	}
 
+	// A map always renders, so /media works even without any media ids.
 	blocks = append(blocks,
-		rich.RelatedArticles(rich.Plain("Related articles"),
-			tg.PageRelatedArticle{URL: "https://telegram.org", Title: "Telegram", Author: "Telegram"},
-		),
-		// A map always renders, so /media works even without any media ids.
 		rich.Map(&tg.InputGeoPoint{Lat: 55.7539, Long: 37.6208}, 15, 600, 400, caption("Red Square")),
 	)
 	return blocks