feat(gateway): add Telegram notification mode to suppress intermediate push notifications

Add a configurable notifications mode for the Telegram platform adapter
that controls which messages trigger push notifications.

- display.platforms.telegram.notifications: "all" (default) | "important"
- HERMES_TELEGRAM_NOTIFICATIONS env var override
- In "important" mode, all sends use disable_notification=True except:
  - Approvals (send_exec_approval) and slash confirmations
  - Final response messages (metadata["notify"]=True)
- Zero overhead in default "all" mode
- Zero impact on non-Telegram platforms

Closes #22771

gateway/run.py

@@ -4649,7 +4649,29 @@ class GatewayRunner:
             if not check_telegram_requirements():
                 logger.warning("Telegram: python-telegram-bot not installed")
                 return None
-            return TelegramAdapter(config)
+            adapter = TelegramAdapter(config)
+            # Apply Telegram notification mode from config.  Controls whether
+            # intermediate messages (tool progress, streaming, status) trigger
+            # push notifications.  Supports ENV override for quick testing.
+            _notify_mode = os.getenv("HERMES_TELEGRAM_NOTIFICATIONS", "")
+            if not _notify_mode:
+                try:
+                    _gw_cfg = _load_gateway_config()
+                    _raw = cfg_get(_gw_cfg, "display", "platforms", "telegram", "notifications")
+                    if _raw not in (None, ""):
+                        _notify_mode = str(_raw).strip().lower()
+                except Exception:
+                    pass
+            _notify_mode = _notify_mode or "all"
+            if _notify_mode not in ("all", "important"):
+                logger.warning(
+                    "Unknown telegram notifications mode '%s', "
+                    "defaulting to 'all' (valid: all, important)",
+                    _notify_mode,
+                )
+                _notify_mode = "all"
+            adapter._notifications_mode = _notify_mode
+            return adapter
         
         elif platform == Platform.DISCORD:
             from gateway.platforms.discord import DiscordAdapter, check_discord_requirements