feat: онбординг после /start — welcome Rich Message + вызов help_command

- help_message.py: добавлен WELCOME_RICH_HTML (приветствие, примеры, скриншоты)
- bot.py: send_rich_help -> send_rich_html(html, stage) + send_rich_message с plain-fallback
- bot.py: start теперь шлёт welcome Rich Message, пауза 0.8с, затем help_command
- help_command вызывает общий send_rich_message — правки HELP_RICH_HTML меняют и онбординг
- тесты: OnboardingTests (3), README/IDEA/VERSION 0.1.0+22

tests/test_release_help.py

@@ -62,5 +62,39 @@ class HelpRoutingTests(unittest.TestCase):
             self.assertIn(term, text)
 
 
+class OnboardingTests(unittest.IsolatedAsyncioTestCase):
+    async def test_start_sends_welcome_rich_then_help_command(self):
+        message = AsyncMock()
+        message.from_user.id = 42
+        message.message_thread_id = None
+        calls: list[str] = []
+
+        async def fake_rich(_message, html, _stage):
+            calls.append(html)
+
+        with (
+            patch.object(bot, "notify_development_deploy", new=AsyncMock()),
+            patch.object(bot, "ensure_subscription"),
+            patch.object(bot.asyncio, "to_thread", new=AsyncMock()),
+            patch.object(bot, "send_rich_message", new=fake_rich),
+        ):
+            await bot.start(message)
+        self.assertEqual(calls, [bot.WELCOME_RICH_HTML, bot.HELP_RICH_HTML])
+
+    async def test_start_help_step_reuses_help_command(self):
+        from pathlib import Path
+
+        source = Path(bot.__file__).read_text(encoding="utf-8")
+        start_body = source.split("async def start(message: Message) -> None:")[1].split("\nasync def ")[0]
+        self.assertIn("await help_command(message)", start_body)
+
+    def test_welcome_message_has_examples_and_help_handoff(self):
+        from help_message import WELCOME_RICH_HTML, rich_to_plain
+
+        text = rich_to_plain(WELCOME_RICH_HTML)
+        for term in ("Привет", "Напиши пост", "скриншот"):
+            self.assertIn(term, text)
+
+
 if __name__ == "__main__":
     unittest.main()