feat(lotus): sendNotificationType=none turns the call-start notification off (cinny #295)

The widget intent presets default sendNotificationType to "notification",
and the URL param could only switch it to ring/notification, so the host
had no way to say "don't notify". In persistent voice channels and space
rooms that notification carries an @room mention: every member got a
highlighted ping (and phone push) whenever a moderator joined first, and
other clients showed it as a missed call.

`sendNotificationType=none` now clears it after the presets are applied.
Unit test added.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_017PCb59uY3UKqDqt7B6hzd5

src/UrlParams.test.ts

@@ -305,6 +305,19 @@ describe("UrlParams", () => {
       });
     });
 
+    it("[lotus] sendNotificationType=none turns the preset notification off", () => {
+      expect(
+        computeUrlParams(
+          "?intent=start_call&widgetId=1234&parentUrl=parent.org&sendNotificationType=none",
+        ).sendNotificationType,
+      ).toBeUndefined();
+      expect(
+        computeUrlParams(
+          "?intent=start_call&widgetId=1234&parentUrl=parent.org",
+        ).sendNotificationType,
+      ).toBe("notification");
+    });
+
     it("accepts join_existing", () => {
       expect(
         computeUrlParams(