feat(telegram): render blockquotes as native <blockquote> tags (#14608) (#14626)

Merged via /review-pr -> /prepare-pr -> /merge-pr.

Prepared head SHA: 4a967c51f5
Co-authored-by: lailoo <20536249+lailoo@users.noreply.github.com>
Co-authored-by: sebslight <19554889+sebslight@users.noreply.github.com>
Reviewed-by: @sebslight

src/telegram/format.test.ts

@@ -37,9 +37,35 @@ describe("markdownToTelegramHtml", () => {
     expect(res).toBe("2. two\n3. three");
   });
 
-  it("flattens headings and blockquotes", () => {
-    const res = markdownToTelegramHtml("# Title\n\n> Quote");
-    expect(res).toBe("Title\n\nQuote");
+  it("flattens headings", () => {
+    const res = markdownToTelegramHtml("# Title");
+    expect(res).toBe("Title");
+  });
+
+  it("renders blockquotes as native Telegram blockquote tags", () => {
+    const res = markdownToTelegramHtml("> Quote");
+    expect(res).toContain("<blockquote>");
+    expect(res).toContain("Quote");
+    expect(res).toContain("</blockquote>");
+  });
+
+  it("renders blockquotes with inline formatting", () => {
+    const res = markdownToTelegramHtml("> **bold** quote");
+    expect(res).toContain("<blockquote>");
+    expect(res).toContain("<b>bold</b>");
+    expect(res).toContain("</blockquote>");
+  });
+
+  it("renders multiline blockquotes as a single Telegram blockquote", () => {
+    const res = markdownToTelegramHtml("> first\n> second");
+    expect(res).toBe("<blockquote>first\nsecond</blockquote>");
+  });
+
+  it("renders separated quoted paragraphs as distinct blockquotes", () => {
+    const res = markdownToTelegramHtml("> first\n\n> second");
+    expect(res).toContain("<blockquote>first");
+    expect(res).toContain("<blockquote>second</blockquote>");
+    expect(res.match(/<blockquote>/g)).toHaveLength(2);
   });
 
   it("renders fenced code blocks", () => {

src/telegram/format.ts

@@ -46,6 +46,7 @@ function renderTelegramHtml(ir: MarkdownIR): string {
       code: { open: "<code>", close: "</code>" },
       code_block: { open: "<pre><code>", close: "</code></pre>" },
       spoiler: { open: "<tg-spoiler>", close: "</tg-spoiler>" },
+      blockquote: { open: "<blockquote>", close: "</blockquote>" },
     },
     escapeText: escapeHtml,
     buildLink: buildTelegramLink,